diff --git a/lib/formdata.c b/lib/formdata.c
index 3568ac579..d0579c52f 100644
--- a/lib/formdata.c
+++ b/lib/formdata.c
@@ -907,7 +907,7 @@ CURLcode Curl_getformdata(struct Curl_easy *data,
         result = curl_mime_headers(part, file->contentheader, 0);
 
       /* Set the content type. */
-      if(!result &&file->contenttype)
+      if(!result && file->contenttype)
         result = curl_mime_type(part, file->contenttype);
 
       /* Set field name. */
diff --git a/lib/mime.c b/lib/mime.c
index cba95b929..1868336ca 100644
--- a/lib/mime.c
+++ b/lib/mime.c
@@ -1619,7 +1619,7 @@ CURLcode Curl_mime_prepare_headers(curl_mimepart *part,
 {
   curl_mime *mime = NULL;
   const char *boundary = NULL;
-  char *s;
+  char *customct;
   const char *cte = NULL;
   CURLcode ret = CURLE_OK;
 
@@ -1631,12 +1631,14 @@ CURLcode Curl_mime_prepare_headers(curl_mimepart *part,
   if(part->state.state == MIMESTATE_CURLHEADERS)
     mimesetstate(&part->state, MIMESTATE_CURLHEADERS, NULL);
 
-  /* Build the content-type header. */
-  s = search_header(part->userheaders, "Content-Type");
-  if(s)
-    contenttype = s;
-  if(part->mimetype)
-    contenttype = part->mimetype;
+  /* Check if content type is specified. */
+  customct = part->mimetype;
+  if(!customct)
+    customct = search_header(part->userheaders, "Content-Type");
+  if(customct)
+    contenttype = customct;
+
+  /* If content type is not specified, try to determine it. */
   if(!contenttype) {
     switch(part->kind) {
     case MIMEKIND_MULTIPART:
@@ -1660,7 +1662,8 @@ CURLcode Curl_mime_prepare_headers(curl_mimepart *part,
     if(mime)
       boundary = mime->boundary;
   }
-  else if(contenttype && strcasecompare(contenttype, "text/plain"))
+  else if(contenttype && !customct &&
+          strcasecompare(contenttype, "text/plain"))
     if(strategy == MIMESTRATEGY_MAIL || !part->filename)
       contenttype = NULL;
 
diff --git a/tests/data/test554 b/tests/data/test554
index ce4a14dc4..24d9c0468 100644
--- a/tests/data/test554
+++ b/tests/data/test554
@@ -68,7 +68,7 @@ s/boundary=------------------------[a-z0-9]*/boundary=--------------------------
 POST /554 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 718
+Content-Length: 744
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------
@@ -87,6 +87,7 @@ Content-Disposition: form-data; name="filename"
 postit2.c
 ------------------------------
 Content-Disposition: form-data; name="submit"
+Content-Type: text/plain
 
 send
 ------------------------------
@@ -98,7 +99,7 @@ blah blah
 POST /554 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 732
+Content-Length: 758
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------
@@ -117,6 +118,7 @@ Content-Disposition: form-data; name="filename"
 postit2.c
 ------------------------------
 Content-Disposition: form-data; name="submit"
+Content-Type: text/plain
 
 send
 ------------------------------
diff --git a/tests/data/test587 b/tests/data/test587
index 5a845d431..0d9530e93 100644
--- a/tests/data/test587
+++ b/tests/data/test587
@@ -43,7 +43,7 @@ s/boundary=------------------------[a-z0-9]*/boundary=--------------------------
 POST /587 HTTP/1.1
 Host: %HOSTIP:%HTTPPORT
 Accept: */*
-Content-Length: 718
+Content-Length: 744
 Content-Type: multipart/form-data; boundary=----------------------------
 
 ------------------------------
diff --git a/tests/data/test650 b/tests/data/test650
index e07d4c10b..1a06064c7 100644
--- a/tests/data/test650
+++ b/tests/data/test650
@@ -63,9 +63,12 @@ Transfer-Encoding: chunked
 Content-Type: multipart/form-data; boundary=----------------------------
 Expect: 100-continue
 
-5f0
+60a
 ------------------------------
 Content-Disposition: form-data; name="fieldname"
+Content-Type: text/plain
+X-customheader-1: Header 1 data
+X-customheader-2: Header 2 data
 
 this is what we post to the silly web server
 ------------------------------
@@ -98,15 +101,13 @@ This is data from a file.
 
 ------------------------------
 Content-Disposition: form-data; name="filecontents"
-X-customheader-1: Header 1 data
-X-customheader-2: Header 2 data
 
 This is data from a file.
 
 ------------------------------
 Content-Disposition: form-data; name="formlength"
 
-1341
+1367
 ------------------------------
 Content-Disposition: form-data; name="standardinput"
 Content-Type: application/octet-stream
diff --git a/tests/libtest/lib554.c b/tests/libtest/lib554.c
index 936d0a10a..cc21d245b 100644
--- a/tests/libtest/lib554.c
+++ b/tests/libtest/lib554.c
@@ -117,7 +117,7 @@ static int once(char *URL, bool oldstyle)
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(1) = %d\n", (int)formrc);
+    printf("curl_formadd(2) = %d\n", (int)formrc);
 
   /* Fill in the filename field */
   formrc = curl_formadd(&formpost,
@@ -134,7 +134,7 @@ static int once(char *URL, bool oldstyle)
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(2) = %d\n", (int)formrc);
+    printf("curl_formadd(3) = %d\n", (int)formrc);
 
   /* Fill in a submit field too */
   formrc = curl_formadd(&formpost,
@@ -147,10 +147,11 @@ static int once(char *URL, bool oldstyle)
 #else
                         CURLFORM_COPYCONTENTS, "send",
 #endif
+                        CURLFORM_CONTENTTYPE, "text/plain",
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(3) = %d\n", (int)formrc);
+    printf("curl_formadd(4) = %d\n", (int)formrc);
 
   formrc = curl_formadd(&formpost, &lastptr,
                         CURLFORM_COPYNAME, "somename",
@@ -160,7 +161,7 @@ static int once(char *URL, bool oldstyle)
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(4) = %d\n", (int)formrc);
+    printf("curl_formadd(5) = %d\n", (int)formrc);
 
   curl = curl_easy_init();
   if(!curl) {
diff --git a/tests/libtest/lib650.c b/tests/libtest/lib650.c
index 130ef1e77..60a2e9f1d 100644
--- a/tests/libtest/lib650.c
+++ b/tests/libtest/lib650.c
@@ -68,10 +68,14 @@ int test(char *URL)
     return TEST_ERR_MAJOR_BAD;
   }
 
-  /* Check proper name and data copying. */
+  /* Check proper name and data copying, as well as headers. */
+  headers = curl_slist_append(headers, "X-customheader-1: Header 1 data");
+  headers = curl_slist_append(headers, "X-customheader-2: Header 2 data");
+  headers = curl_slist_append(headers, "Content-Type: text/plain");
   formrc = curl_formadd(&formpost, &lastptr,
                         CURLFORM_COPYNAME, &name,
                         CURLFORM_COPYCONTENTS, &data,
+                        CURLFORM_CONTENTHEADER, headers,
                         CURLFORM_END);
 
   if(formrc)
@@ -113,18 +117,15 @@ int test(char *URL)
   if(formrc)
     printf("curl_formadd(3) = %d\n", (int) formrc);
 
-  /* Check data from file content and headers. */
-  headers = curl_slist_append(headers, "X-customheader-1: Header 1 data");
-  headers = curl_slist_append(headers, "X-customheader-2: Header 2 data");
+  /* Check data from file content. */
   formrc = curl_formadd(&formpost,
                         &lastptr,
                         CURLFORM_COPYNAME, "filecontents",
                         CURLFORM_FILECONTENT, libtest_arg2,
-                        CURLFORM_CONTENTHEADER, headers,
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(3) = %d\n", (int) formrc);
+    printf("curl_formadd(4) = %d\n", (int) formrc);
 
   /* Measure the current form length.
    * This is done before including stdin data because we want to reuse it
@@ -148,7 +149,7 @@ int test(char *URL)
                         CURLFORM_END);
 
   if(formrc)
-    printf("curl_formadd(4) = %d\n", (int) formrc);
+    printf("curl_formadd(5) = %d\n", (int) formrc);
 
   curl = curl_easy_init();
   if(!curl) {