diff --git a/lib/asyn-thread.c b/lib/asyn-thread.c
index 7c8598274..4f4685070 100644
--- a/lib/asyn-thread.c
+++ b/lib/asyn-thread.c
@@ -711,7 +711,7 @@ struct Curl_addrinfo *Curl_resolver_getaddrinfo(struct connectdata *conn,
     return NULL;
   }
 
-  failf(conn->data, "getaddrinfo() thread failed\n");
+  failf(conn->data, "getaddrinfo() thread failed");
 
   return NULL;
 }
@@ -766,7 +766,7 @@ struct Curl_addrinfo *Curl_resolver_getaddrinfo(struct connectdata *conn,
     return NULL;
   }
 
-  failf(data, "getaddrinfo() thread failed to start\n");
+  failf(data, "getaddrinfo() thread failed to start");
   return NULL;
 
 }
diff --git a/lib/c-hyper.c b/lib/c-hyper.c
index c7995d9f1..5df2f0e19 100644
--- a/lib/c-hyper.c
+++ b/lib/c-hyper.c
@@ -340,7 +340,7 @@ static CURLcode hyperstream(struct Curl_easy *data,
     h->init = TRUE;
     *didwhat = KEEP_RECV;
     if(!resp) {
-      failf(data, "hyperstream: couldn't get response\n");
+      failf(data, "hyperstream: couldn't get response");
       return CURLE_RECV_ERROR;
     }
 
@@ -356,7 +356,7 @@ static CURLcode hyperstream(struct Curl_easy *data,
 
     headers = hyper_response_headers(resp);
     if(!headers) {
-      failf(data, "hyperstream: couldn't get response headers\n");
+      failf(data, "hyperstream: couldn't get response headers");
       result = CURLE_RECV_ERROR;
       break;
     }
@@ -369,20 +369,20 @@ static CURLcode hyperstream(struct Curl_easy *data,
     }
 
     if(empty_header(data)) {
-      failf(data, "hyperstream: couldn't pass blank header\n");
+      failf(data, "hyperstream: couldn't pass blank header");
       result = CURLE_OUT_OF_MEMORY;
       break;
     }
 
     resp_body = hyper_response_body(resp);
     if(!resp_body) {
-      failf(data, "hyperstream: couldn't get response body\n");
+      failf(data, "hyperstream: couldn't get response body");
       result = CURLE_RECV_ERROR;
       break;
     }
     foreach = hyper_body_foreach(resp_body, hyper_body_chunk, data);
     if(!foreach) {
-      failf(data, "hyperstream: body foreach failed\n");
+      failf(data, "hyperstream: body foreach failed");
       result = CURLE_OUT_OF_MEMORY;
       break;
     }
@@ -467,7 +467,7 @@ CURLcode Curl_hyper_header(struct Curl_easy *data, hyper_headers *headers,
 
     if(HYPERE_OK != hyper_headers_add(headers, (uint8_t *)n, nlen,
                                       (uint8_t *)v, vlen)) {
-      failf(data, "hyper_headers_add host\n");
+      failf(data, "hyper_headers_add host");
       return CURLE_OUT_OF_MEMORY;
     }
     if(data->set.verbose) {
@@ -505,7 +505,7 @@ static CURLcode request_target(struct Curl_easy *data,
 
   if(hyper_request_set_uri(req, (uint8_t *)Curl_dyn_uptr(&r),
                            Curl_dyn_len(&r))) {
-    failf(data, "error setting path\n");
+    failf(data, "error setting path");
     result = CURLE_OUT_OF_MEMORY;
   }
   else
@@ -758,7 +758,7 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
 
   headers = hyper_request_headers(req);
   if(!headers) {
-    failf(data, "hyper_request_headers\n");
+    failf(data, "hyper_request_headers");
     goto error;
   }
 
@@ -829,7 +829,7 @@ CURLcode Curl_http(struct connectdata *conn, bool *done)
   data->req.upload_chunky = FALSE;
   sendtask = hyper_clientconn_send(client, req);
   if(!sendtask) {
-    failf(data, "hyper_clientconn_send\n");
+    failf(data, "hyper_clientconn_send");
     goto error;
   }
 
diff --git a/lib/doh.c b/lib/doh.c
index c2b76de53..41d34dd30 100644
--- a/lib/doh.c
+++ b/lib/doh.c
@@ -225,7 +225,7 @@ static CURLcode dohprobe(struct Curl_easy *data,
   DOHcode d = doh_encode(host, dnstype, p->dohbuffer, sizeof(p->dohbuffer),
                          &p->dohlen);
   if(d) {
-    failf(data, "Failed to encode DOH packet [%d]\n", d);
+    failf(data, "Failed to encode DOH packet [%d]", d);
     return CURLE_OUT_OF_MEMORY;
   }
 
diff --git a/lib/ftp.c b/lib/ftp.c
index bc3557421..74f9e020a 100644
--- a/lib/ftp.c
+++ b/lib/ftp.c
@@ -1768,7 +1768,7 @@ static CURLcode ftp_epsv_disable(struct connectdata *conn)
 #endif
     ) {
     /* We can't disable EPSV when doing IPv6, so this is instead a fail */
-    failf(conn->data, "Failed EPSV attempt, exiting\n");
+    failf(conn->data, "Failed EPSV attempt, exiting");
     return CURLE_WEIRD_SERVER_REPLY;
   }
 
diff --git a/lib/http.c b/lib/http.c
index 3f7f4ba21..691c0937f 100644
--- a/lib/http.c
+++ b/lib/http.c
@@ -3743,7 +3743,7 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
           k->badheader = HEADER_ALLBAD;
           streamclose(conn, "bad HTTP: No end-of-message indicator");
           if(!data->set.http09_allowed) {
-            failf(data, "Received HTTP/0.9 when not allowed\n");
+            failf(data, "Received HTTP/0.9 when not allowed");
             return CURLE_UNSUPPORTED_PROTOCOL;
           }
           break;
@@ -3778,7 +3778,7 @@ CURLcode Curl_http_readwrite_headers(struct Curl_easy *data,
         streamclose(conn, "bad HTTP: No end-of-message indicator");
         /* this is not the beginning of a protocol first header line */
         if(!data->set.http09_allowed) {
-          failf(data, "Received HTTP/0.9 when not allowed\n");
+          failf(data, "Received HTTP/0.9 when not allowed");
           return CURLE_UNSUPPORTED_PROTOCOL;
         }
         k->header = FALSE;
diff --git a/lib/http2.c b/lib/http2.c
index 7a337a7f3..7ed708e10 100644
--- a/lib/http2.c
+++ b/lib/http2.c
@@ -542,7 +542,7 @@ static int push_promise(struct Curl_easy *data,
 
     stream = data->req.p.http;
     if(!stream) {
-      failf(data, "Internal NULL stream!\n");
+      failf(data, "Internal NULL stream!");
       (void)Curl_close(&newhandle);
       rv = CURL_PUSH_DENY;
       goto fail;
@@ -957,7 +957,7 @@ static int on_header(nghttp2_session *session, const nghttp2_frame *frame,
 
   stream = data_s->req.p.http;
   if(!stream) {
-    failf(data_s, "Internal NULL stream! 5\n");
+    failf(data_s, "Internal NULL stream!");
     return NGHTTP2_ERR_CALLBACK_FAILURE;
   }
 
@@ -1341,7 +1341,7 @@ static int h2_process_pending_input(struct connectdata *conn,
   if(rv < 0) {
     failf(data,
           "h2_process_pending_input: nghttp2_session_mem_recv() returned "
-          "%zd:%s\n", rv, nghttp2_strerror((int)rv));
+          "%zd:%s", rv, nghttp2_strerror((int)rv));
     *err = CURLE_RECV_ERROR;
     return -1;
   }
diff --git a/lib/imap.c b/lib/imap.c
index c6dd7a232..75ab77dca 100644
--- a/lib/imap.c
+++ b/lib/imap.c
@@ -769,7 +769,7 @@ static CURLcode imap_perform_append(struct connectdata *conn)
 
   /* Check we know the size of the upload */
   if(data->state.infilesize < 0) {
-    failf(data, "Cannot APPEND with unknown input file size\n");
+    failf(data, "Cannot APPEND with unknown input file size");
     return CURLE_UPLOAD_FAILED;
   }
 
diff --git a/lib/sendf.c b/lib/sendf.c
index 04cc725f5..adcee89f8 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -267,6 +267,7 @@ void Curl_infof(struct Curl_easy *data, const char *fmt, ...)
 
 void Curl_failf(struct Curl_easy *data, const char *fmt, ...)
 {
+  DEBUGASSERT(!strchr(fmt, '\n'));
   if(data->set.verbose || data->set.errorbuffer) {
     va_list ap;
     size_t len;
diff --git a/lib/socks.c b/lib/socks.c
index a2d1e621f..301c6a966 100644
--- a/lib/socks.c
+++ b/lib/socks.c
@@ -298,7 +298,7 @@ CURLproxycode Curl_SOCKS4(const char *proxy_user,
       }
       else {
         hp = NULL; /* fail! */
-        failf(data, "SOCKS4 connection to %s not supported\n", buf);
+        failf(data, "SOCKS4 connection to %s not supported", buf);
       }
 
       Curl_resolv_unlock(data, dns); /* not used anymore from now on */
@@ -319,7 +319,7 @@ CURLproxycode Curl_SOCKS4(const char *proxy_user,
     if(proxy_user) {
       size_t plen = strlen(proxy_user);
       if(plen >= sizeof(sx->socksreq) - 8) {
-        failf(data, "Too long SOCKS proxy user name, can't use!\n");
+        failf(data, "Too long SOCKS proxy user name, can't use!");
         return CURLPX_LONG_USER;
       }
       /* copy the proxy name WITH trailing zero */
@@ -839,7 +839,7 @@ CURLproxycode Curl_SOCKS5(const char *proxy_user,
 #endif
     else {
       hp = NULL; /* fail! */
-      failf(data, "SOCKS5 connection to %s not supported\n", dest);
+      failf(data, "SOCKS5 connection to %s not supported", dest);
     }
 
     Curl_resolv_unlock(data, dns); /* not used anymore from now on */
diff --git a/lib/socks_gssapi.c b/lib/socks_gssapi.c
index a96579692..9d37b9bd9 100644
--- a/lib/socks_gssapi.c
+++ b/lib/socks_gssapi.c
@@ -92,7 +92,7 @@ static int check_gss_err(struct Curl_easy *data,
       }
       gss_release_buffer(&min_stat, &status_string);
     }
-    failf(data, "GSS-API error: %s failed:\n%s", function, buf);
+    failf(data, "GSS-API error: %s failed: %s", function, buf);
     return 1;
   }
 
diff --git a/lib/tftp.c b/lib/tftp.c
index fba3f5e8c..ba7c38b25 100644
--- a/lib/tftp.c
+++ b/lib/tftp.c
@@ -493,7 +493,7 @@ static CURLcode tftp_send_first(struct tftp_state_data *state,
       return result;
 
     if(strlen(filename) > (state->blksize - strlen(mode) - 4)) {
-      failf(data, "TFTP file name too long\n");
+      failf(data, "TFTP file name too long");
       free(filename);
       return CURLE_TFTP_ILLEGAL; /* too long file name field */
     }
diff --git a/lib/url.c b/lib/url.c
index a340213ad..b998c5efb 100644
--- a/lib/url.c
+++ b/lib/url.c
@@ -1550,7 +1550,7 @@ CURLcode Curl_idnconvert_hostname(struct connectdata *conn,
         host->name = host->encalloc;
       }
       else {
-        failf(data, "Failed to convert %s to ACE; %s\n", host->name,
+        failf(data, "Failed to convert %s to ACE; %s", host->name,
               idn2_strerror(rc));
         return CURLE_URL_MALFORMAT;
       }
@@ -1565,7 +1565,7 @@ CURLcode Curl_idnconvert_hostname(struct connectdata *conn,
     }
     else {
       char buffer[STRERROR_LEN];
-      failf(data, "Failed to convert %s to ACE; %s\n", host->name,
+      failf(data, "Failed to convert %s to ACE; %s", host->name,
             Curl_winapi_strerror(GetLastError(), buffer, sizeof(buffer)));
       return CURLE_URL_MALFORMAT;
     }
diff --git a/lib/vauth/digest_sspi.c b/lib/vauth/digest_sspi.c
index f07581ec7..dad947a37 100644
--- a/lib/vauth/digest_sspi.c
+++ b/lib/vauth/digest_sspi.c
@@ -135,7 +135,7 @@ CURLcode Curl_auth_create_digest_md5_message(struct Curl_easy *data,
   if(status != SEC_E_OK) {
     free(input_token);
 
-    failf(data, "SSPI: couldn't get auth info\n");
+    failf(data, "SSPI: couldn't get auth info");
     return CURLE_AUTH_ERROR;
   }
 
@@ -439,7 +439,7 @@ CURLcode Curl_auth_create_digest_http_message(struct Curl_easy *data,
   status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_DIGEST),
                                               &SecurityPackage);
   if(status != SEC_E_OK) {
-    failf(data, "SSPI: couldn't get auth info\n");
+    failf(data, "SSPI: couldn't get auth info");
     return CURLE_AUTH_ERROR;
   }
 
diff --git a/lib/vauth/krb5_sspi.c b/lib/vauth/krb5_sspi.c
index 8e56a8240..b2d163534 100644
--- a/lib/vauth/krb5_sspi.c
+++ b/lib/vauth/krb5_sspi.c
@@ -125,7 +125,7 @@ CURLcode Curl_auth_create_gssapi_user_message(struct Curl_easy *data,
                                                 TEXT(SP_NAME_KERBEROS),
                                                 &SecurityPackage);
     if(status != SEC_E_OK) {
-      failf(data, "SSPI: couldn't get auth info\n");
+      failf(data, "SSPI: couldn't get auth info");
       return CURLE_AUTH_ERROR;
     }
 
diff --git a/lib/vauth/ntlm_sspi.c b/lib/vauth/ntlm_sspi.c
index 28bc3efda..07dc97398 100644
--- a/lib/vauth/ntlm_sspi.c
+++ b/lib/vauth/ntlm_sspi.c
@@ -106,7 +106,7 @@ CURLcode Curl_auth_create_ntlm_type1_message(struct Curl_easy *data,
   status = s_pSecFn->QuerySecurityPackageInfo((TCHAR *) TEXT(SP_NAME_NTLM),
                                               &SecurityPackage);
   if(status != SEC_E_OK) {
-    failf(data, "SSPI: couldn't get auth info\n");
+    failf(data, "SSPI: couldn't get auth info");
     return CURLE_AUTH_ERROR;
   }
 
diff --git a/lib/vauth/spnego_sspi.c b/lib/vauth/spnego_sspi.c
index e7482a43e..4aa1ba957 100644
--- a/lib/vauth/spnego_sspi.c
+++ b/lib/vauth/spnego_sspi.c
@@ -130,7 +130,7 @@ CURLcode Curl_auth_decode_spnego_message(struct Curl_easy *data,
                                                       TEXT(SP_NAME_NEGOTIATE),
                                                       &SecurityPackage);
     if(nego->status != SEC_E_OK) {
-      failf(data, "SSPI: couldn't get auth info\n");
+      failf(data, "SSPI: couldn't get auth info");
       return CURLE_AUTH_ERROR;
     }
 
diff --git a/lib/vquic/ngtcp2.c b/lib/vquic/ngtcp2.c
index 5a017b622..3b401ef15 100644
--- a/lib/vquic/ngtcp2.c
+++ b/lib/vquic/ngtcp2.c
@@ -587,7 +587,7 @@ static int cb_recv_stream_data(ngtcp2_conn *tconn, uint32_t flags,
   nconsumed =
     nghttp3_conn_read_stream(qs->h3conn, stream_id, buf, buflen, fin);
   if(nconsumed < 0) {
-    failf(qs->conn->data, "nghttp3_conn_read_stream returned error: %s\n",
+    failf(qs->conn->data, "nghttp3_conn_read_stream returned error: %s",
           nghttp3_strerror((int)nconsumed));
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
@@ -616,7 +616,7 @@ cb_acked_stream_data_offset(ngtcp2_conn *tconn, int64_t stream_id,
 
   rv = nghttp3_conn_add_ack_offset(qs->h3conn, stream_id, datalen);
   if(rv != 0) {
-    failf(qs->conn->data, "nghttp3_conn_add_ack_offset returned error: %s\n",
+    failf(qs->conn->data, "nghttp3_conn_add_ack_offset returned error: %s",
           nghttp3_strerror(rv));
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
@@ -637,7 +637,7 @@ static int cb_stream_close(ngtcp2_conn *tconn, int64_t stream_id,
   rv = nghttp3_conn_close_stream(qs->h3conn, stream_id,
                                  app_error_code);
   if(rv != 0) {
-    failf(qs->conn->data, "nghttp3_conn_close_stream returned error: %s\n",
+    failf(qs->conn->data, "nghttp3_conn_close_stream returned error: %s",
           nghttp3_strerror(rv));
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
@@ -658,7 +658,7 @@ static int cb_stream_reset(ngtcp2_conn *tconn, int64_t stream_id,
 
   rv = nghttp3_conn_reset_stream(qs->h3conn, stream_id);
   if(rv != 0) {
-    failf(qs->conn->data, "nghttp3_conn_reset_stream returned error: %s\n",
+    failf(qs->conn->data, "nghttp3_conn_reset_stream returned error: %s",
           nghttp3_strerror(rv));
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
@@ -689,7 +689,7 @@ static int cb_extend_max_stream_data(ngtcp2_conn *tconn, int64_t stream_id,
 
   rv = nghttp3_conn_unblock_stream(qs->h3conn, stream_id);
   if(rv != 0) {
-    failf(qs->conn->data, "nghttp3_conn_unblock_stream returned error: %s\n",
+    failf(qs->conn->data, "nghttp3_conn_unblock_stream returned error: %s",
           nghttp3_strerror(rv));
     return NGTCP2_ERR_CALLBACK_FAILURE;
   }
@@ -1783,7 +1783,7 @@ static CURLcode ng_flush_egress(struct connectdata *conn, int sockfd,
 
   rv = ngtcp2_conn_handle_expiry(qs->qconn, ts);
   if(rv != 0) {
-    failf(conn->data, "ngtcp2_conn_handle_expiry returned error: %s\n",
+    failf(conn->data, "ngtcp2_conn_handle_expiry returned error: %s",
           ngtcp2_strerror(rv));
     return CURLE_SEND_ERROR;
   }
@@ -1796,7 +1796,7 @@ static CURLcode ng_flush_egress(struct connectdata *conn, int sockfd,
       veccnt = nghttp3_conn_writev_stream(qs->h3conn, &stream_id, &fin, vec,
                                           sizeof(vec) / sizeof(vec[0]));
       if(veccnt < 0) {
-        failf(conn->data, "nghttp3_conn_writev_stream returned error: %s\n",
+        failf(conn->data, "nghttp3_conn_writev_stream returned error: %s",
               nghttp3_strerror((int)veccnt));
         return CURLE_SEND_ERROR;
       }
@@ -1838,7 +1838,7 @@ static CURLcode ng_flush_egress(struct connectdata *conn, int sockfd,
           }
           else {
             assert(ndatalen == -1);
-            failf(conn->data, "ngtcp2_conn_writev_stream returned error: %s\n",
+            failf(conn->data, "ngtcp2_conn_writev_stream returned error: %s",
                   ngtcp2_strerror((int)outlen));
             return CURLE_SEND_ERROR;
           }
@@ -1852,7 +1852,7 @@ static CURLcode ng_flush_egress(struct connectdata *conn, int sockfd,
       outlen = ngtcp2_conn_write_pkt(qs->qconn, &ps.path, NULL,
                                      out, pktlen, ts);
       if(outlen < 0) {
-        failf(conn->data, "ngtcp2_conn_write_pkt returned error: %s\n",
+        failf(conn->data, "ngtcp2_conn_write_pkt returned error: %s",
               ngtcp2_strerror((int)outlen));
         return CURLE_SEND_ERROR;
       }
@@ -1871,7 +1871,7 @@ static CURLcode ng_flush_egress(struct connectdata *conn, int sockfd,
         break;
       }
       else {
-        failf(conn->data, "send() returned %zd (errno %d)\n", sent,
+        failf(conn->data, "send() returned %zd (errno %d)", sent,
               SOCKERRNO);
         return CURLE_SEND_ERROR;
       }
diff --git a/lib/vquic/quiche.c b/lib/vquic/quiche.c
index 3e913ec79..a66b66447 100644
--- a/lib/vquic/quiche.c
+++ b/lib/vquic/quiche.c
@@ -399,14 +399,14 @@ static CURLcode flush_egress(struct connectdata *conn, int sockfd,
       break;
 
     if(sent < 0) {
-      failf(conn->data, "quiche_conn_send returned %zd\n",
+      failf(conn->data, "quiche_conn_send returned %zd",
             sent);
       return CURLE_SEND_ERROR;
     }
 
     sent = send(sockfd, out, sent, 0);
     if(sent < 0) {
-      failf(conn->data, "send() returned %zd\n", sent);
+      failf(conn->data, "send() returned %zd", sent);
       return CURLE_SEND_ERROR;
     }
   } while(1);
diff --git a/lib/vssh/libssh2.c b/lib/vssh/libssh2.c
index a69bcda99..b44c9d232 100644
--- a/lib/vssh/libssh2.c
+++ b/lib/vssh/libssh2.c
@@ -763,10 +763,10 @@ static CURLcode ssh_force_knownhost_key_type(struct connectdata *conn)
         hostkey_method = hostkey_method_ssh_dss;
         break;
       case LIBSSH2_KNOWNHOST_KEY_RSA1:
-        failf(data, "Found host key type RSA1 which is not supported\n");
+        failf(data, "Found host key type RSA1 which is not supported");
         return CURLE_SSH;
       default:
-        failf(data, "Unknown host key type: %i\n",
+        failf(data, "Unknown host key type: %i",
               (store->typemask & LIBSSH2_KNOWNHOST_KEY_MASK));
         return CURLE_SSH;
       }
diff --git a/lib/vssh/wolfssh.c b/lib/vssh/wolfssh.c
index b0dfb2047..5dd95546c 100644
--- a/lib/vssh/wolfssh.c
+++ b/lib/vssh/wolfssh.c
@@ -262,7 +262,7 @@ static ssize_t wsftp_send(struct connectdata *conn, int sockindex,
     return -1;
   }
   if(rc < 0) {
-    failf(conn->data, "wolfSSH_SFTP_SendWritePacket returned %d\n", rc);
+    failf(conn->data, "wolfSSH_SFTP_SendWritePacket returned %d", rc);
     return -1;
   }
   DEBUGASSERT(rc == (int)len);
@@ -307,7 +307,7 @@ static ssize_t wsftp_recv(struct connectdata *conn, int sockindex,
   DEBUGASSERT(rc <= (int)len);
 
   if(rc < 0) {
-    failf(conn->data, "wolfSSH_SFTP_SendReadPacket returned %d\n", rc);
+    failf(conn->data, "wolfSSH_SFTP_SendReadPacket returned %d", rc);
     return -1;
   }
   sshc->offset += len;
diff --git a/lib/vtls/bearssl.c b/lib/vtls/bearssl.c
index b0c3dc2f0..421c1451f 100644
--- a/lib/vtls/bearssl.c
+++ b/lib/vtls/bearssl.c
@@ -349,8 +349,8 @@ static CURLcode bearssl_connect_step1(struct connectdata *conn, int sockindex)
     ret = load_cafile(ssl_cafile, &backend->anchors, &backend->anchors_len);
     if(ret != CURLE_OK) {
       if(verifypeer) {
-        failf(data, "error setting certificate verify locations:\n"
-              "  CAfile: %s\n", ssl_cafile);
+        failf(data, "error setting certificate verify locations."
+              " CAfile: %s", ssl_cafile);
         return ret;
       }
       infof(data, "error setting certificate verify locations,"
diff --git a/lib/vtls/mbedtls.c b/lib/vtls/mbedtls.c
index 191315df8..e130f192d 100644
--- a/lib/vtls/mbedtls.c
+++ b/lib/vtls/mbedtls.c
@@ -280,7 +280,7 @@ mbed_connect_step1(struct connectdata *conn,
 #ifdef MBEDTLS_ERROR_C
     mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
 #endif /* MBEDTLS_ERROR_C */
-    failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s\n",
+    failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
           -ret, errorbuf);
   }
 #else
@@ -293,7 +293,7 @@ mbed_connect_step1(struct connectdata *conn,
 #ifdef MBEDTLS_ERROR_C
     mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
 #endif /* MBEDTLS_ERROR_C */
-    failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s\n",
+    failf(data, "Failed - mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
           -ret, errorbuf);
   }
 #endif /* THREADING_SUPPORT */
@@ -868,7 +868,7 @@ static CURLcode Curl_mbedtls_random(struct Curl_easy *data,
 #ifdef MBEDTLS_ERROR_C
     mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
 #endif /* MBEDTLS_ERROR_C */
-    failf(data, "Failed - mbedTLS: ctr_drbg_seed returned (-0x%04X) %s\n",
+    failf(data, "Failed - mbedTLS: ctr_drbg_seed returned (-0x%04X) %s",
           -ret, errorbuf);
   }
   else {
@@ -878,7 +878,7 @@ static CURLcode Curl_mbedtls_random(struct Curl_easy *data,
 #ifdef MBEDTLS_ERROR_C
       mbedtls_strerror(ret, errorbuf, sizeof(errorbuf));
 #endif /* MBEDTLS_ERROR_C */
-      failf(data, "mbedTLS: ctr_drbg_init returned (-0x%04X) %s\n",
+      failf(data, "mbedTLS: ctr_drbg_init returned (-0x%04X) %s",
             -ret, errorbuf);
     }
   }
diff --git a/lib/vtls/openssl.c b/lib/vtls/openssl.c
index e9c535f8f..dfb5ed54d 100644
--- a/lib/vtls/openssl.c
+++ b/lib/vtls/openssl.c
@@ -1289,7 +1289,7 @@ static CURLcode Curl_ossl_set_engine(struct Curl_easy *data,
     char buf[256];
 
     ENGINE_free(e);
-    failf(data, "Failed to initialise SSL Engine '%s':\n%s",
+    failf(data, "Failed to initialise SSL Engine '%s': %s",
           engine, ossl_strerror(ERR_get_error(), buf, sizeof(buf)));
     return CURLE_SSL_ENGINE_INITFAILED;
   }
diff --git a/lib/vtls/wolfssl.c b/lib/vtls/wolfssl.c
index 44ee2d9ec..3f5f0949e 100644
--- a/lib/vtls/wolfssl.c
+++ b/lib/vtls/wolfssl.c
@@ -608,7 +608,7 @@ wolfssl_connect_step2(struct connectdata *conn,
      * as also mismatching CN fields */
     else if(DOMAIN_NAME_MISMATCH == detail) {
 #if 1
-      failf(data, "\tsubject alt name(s) or common name do not match \"%s\"\n",
+      failf(data, "\tsubject alt name(s) or common name do not match \"%s\"",
             dispname);
       return CURLE_PEER_FAILED_VERIFICATION;
 #else
@@ -635,7 +635,7 @@ wolfssl_connect_step2(struct connectdata *conn,
 #if LIBWOLFSSL_VERSION_HEX >= 0x02007000 /* 2.7.0 */
     else if(ASN_NO_SIGNER_E == detail) {
       if(SSL_CONN_CONFIG(verifypeer)) {
-        failf(data, "\tCA signer not available for verification\n");
+        failf(data, "\tCA signer not available for verification");
         return CURLE_SSL_CACERT_BADFILE;
       }
       else {