diff --git a/lib/content_encoding.c b/lib/content_encoding.c
index 77814ac30..a84ff543b 100644
--- a/lib/content_encoding.c
+++ b/lib/content_encoding.c
@@ -985,7 +985,8 @@ new_unencoding_writer(struct Curl_easy *data,
   return writer;
 }
 
-/* Write data using an unencoding writer stack. */
+/* Write data using an unencoding writer stack. "nbytes" is not
+   allowed to be 0. */
 CURLcode Curl_unencode_write(struct Curl_easy *data,
                              struct contenc_writer *writer,
                              const char *buf, size_t nbytes)
diff --git a/lib/pop3.c b/lib/pop3.c
index ccfebd02a..275ffeada 100644
--- a/lib/pop3.c
+++ b/lib/pop3.c
@@ -1515,8 +1515,17 @@ CURLcode Curl_pop3_write(struct Curl_easy *data, char *str, size_t nread)
       if(prev) {
         /* If the partial match was the CRLF and dot then only write the CRLF
            as the server would have inserted the dot */
-        result = Curl_client_write(data, CLIENTWRITE_BODY, (char *)POP3_EOB,
-                                   strip_dot ? prev - 1 : prev);
+        if(strip_dot && prev - 1 > 0) {
+          result = Curl_client_write(data, CLIENTWRITE_BODY, (char *)POP3_EOB,
+                                     prev - 1);
+        }
+        else if(!strip_dot) {
+          result = Curl_client_write(data, CLIENTWRITE_BODY, (char *)POP3_EOB,
+                                     prev);
+        }
+        else {
+          result = CURLE_OK;
+        }
 
         if(result)
           return result;
diff --git a/lib/sendf.c b/lib/sendf.c
index 17d3d51e3..fa3c5a35d 100644
--- a/lib/sendf.c
+++ b/lib/sendf.c
@@ -604,7 +604,7 @@ static CURLcode chop_write(struct Curl_easy *data,
 /* Curl_client_write() sends data to the write callback(s)
 
    The bit pattern defines to what "streams" to write to. Body and/or header.
-   The defines are in sendf.h of course.
+   The defines are in sendf.h of course. "len" is not allowed to be 0.
 
    If CURL_DO_LINEEND_CONV is enabled, data is converted IN PLACE to the
    local character encoding.  This is a problem and should be changed in
diff --git a/lib/transfer.c b/lib/transfer.c
index 56ad5e612..c31e22e00 100644
--- a/lib/transfer.c
+++ b/lib/transfer.c
@@ -830,7 +830,7 @@ static CURLcode readwrite_data(struct Curl_easy *data,
              Make sure that ALL_CONTENT_ENCODINGS contains all the
              encodings handled here. */
           if(data->set.http_ce_skip || !k->writer_stack) {
-            if(!k->ignorebody) {
+            if(!k->ignorebody && nread) {
 #ifndef CURL_DISABLE_POP3
               if(conn->handler->protocol & PROTO_FAMILY_POP3)
                 result = Curl_pop3_write(data, k->str, nread);
@@ -840,7 +840,7 @@ static CURLcode readwrite_data(struct Curl_easy *data,
                                            nread);
             }
           }
-          else if(!k->ignorebody)
+          else if(!k->ignorebody && nread)
             result = Curl_unencode_write(data, k->writer_stack, k->str, nread);
         }
         k->badheader = HEADER_NORMAL; /* taken care of now */