diff --git a/dlls/winhttp/main.c b/dlls/winhttp/main.c
index 192ec214a49..fb66360c9bc 100644
--- a/dlls/winhttp/main.c
+++ b/dlls/winhttp/main.c
@@ -293,3 +293,15 @@ BOOL WINAPI WinHttpQueryHeaders (HINTERNET hRequest, DWORD dwInfoLevel, LPCWSTR
     SetLastError(ERROR_NOT_SUPPORTED);
     return FALSE;
 }
+
+/***********************************************************************
+ *          WinHttpAddRequestHeaders (winhttp.@)
+ */
+BOOL WINAPI WinHttpAddRequestHeaders (HINTERNET hRequest, LPCWSTR pwszHeaders,
+                                      DWORD dwHeadersLength, DWORD dwModifiers)
+{
+    FIXME("(%s, %d, %d): stub\n", debugstr_w(pwszHeaders), dwHeadersLength, dwModifiers);
+
+    SetLastError(ERROR_NOT_SUPPORTED);
+    return FALSE;
+}
diff --git a/dlls/winhttp/winhttp.spec b/dlls/winhttp/winhttp.spec
index fc82609e8a8..ce9407e1bcc 100644
--- a/dlls/winhttp/winhttp.spec
+++ b/dlls/winhttp/winhttp.spec
@@ -2,7 +2,7 @@
 @ stdcall -private DllGetClassObject(ptr ptr ptr)
 @ stdcall -private DllRegisterServer()
 @ stdcall -private DllUnregisterServer()
-@ stub WinHttpAddRequestHeaders
+@ stdcall WinHttpAddRequestHeaders(ptr wstr long long)
 @ stdcall WinHttpCheckPlatform()
 @ stdcall WinHttpCloseHandle(ptr)
 @ stdcall WinHttpConnect(ptr wstr long long)