diff --git a/modules/juce_core/network/juce_URL.cpp b/modules/juce_core/network/juce_URL.cpp
index fc46865c5e..b8ddb2abfa 100644
--- a/modules/juce_core/network/juce_URL.cpp
+++ b/modules/juce_core/network/juce_URL.cpp
@@ -198,9 +198,11 @@ namespace URLHelpers
             data << getMangledParameters (url)
                  << url.getPostData();
 
-            // just a short text attachment, so use simple url encoding..
-            headers << "Content-Type: application/x-www-form-urlencoded\r\nContent-length: "
-                    << (int) data.getDataSize() << "\r\n";
+            // if the user-supplied headers didn't contain a content-type, add one now..
+            if (! headers.containsIgnoreCase ("Content-Type"))
+                headers << "Content-Type: application/x-www-form-urlencoded\r\n";
+
+            headers << "Content-length: " << (int) data.getDataSize() << "\r\n";
         }
     }
 
@@ -320,18 +322,18 @@ bool URL::isProbablyAnEmailAddress (const String& possibleEmailAddress)
 InputStream* URL::createInputStream (const bool usePostCommand,
                                      OpenStreamProgressCallback* const progressCallback,
                                      void* const progressCallbackContext,
-                                     const String& extraHeaders,
+                                     String headers,
                                      const int timeOutMs,
                                      StringPairArray* const responseHeaders) const
 {
-    String headers;
     MemoryBlock headersAndPostData;
 
+    if (! headers.endsWithChar ('\n'))
+        headers << "\r\n";
+
     if (usePostCommand)
         URLHelpers::createHeadersAndPostData (*this, headers, headersAndPostData);
 
-    headers += extraHeaders;
-
     if (! headers.endsWithChar ('\n'))
         headers << "\r\n";
 
diff --git a/modules/juce_core/network/juce_URL.h b/modules/juce_core/network/juce_URL.h
index 9381fa6ecb..82ae5880aa 100644
--- a/modules/juce_core/network/juce_URL.h
+++ b/modules/juce_core/network/juce_URL.h
@@ -251,7 +251,7 @@ public:
     InputStream* createInputStream (bool usePostCommand,
                                     OpenStreamProgressCallback* progressCallback = nullptr,
                                     void* progressCallbackContext = nullptr,
-                                    const String& extraHeaders = String::empty,
+                                    String extraHeaders = String::empty,
                                     int connectionTimeOutMs = 0,
                                     StringPairArray* responseHeaders = nullptr) const;