diff --git a/dlls/winhttp/main.c b/dlls/winhttp/main.c
index a87d5ab4de4..82f0a618f2c 100644
--- a/dlls/winhttp/main.c
+++ b/dlls/winhttp/main.c
@@ -94,17 +94,6 @@ BOOL WINAPI WinHttpQueryOption (HINTERNET hInternet, DWORD dwOption, LPVOID lpBu
     return FALSE;
 }
 
-/***********************************************************************
- *          WinHttpQueryDataAvailable (winhttp.@)
- */
-BOOL WINAPI WinHttpQueryDataAvailable (HINTERNET hInternet, LPDWORD lpdwNumberOfBytesAvailable)
-{
-    FIXME("stub\n");
-
-    SetLastError(ERROR_NOT_SUPPORTED);
-    return FALSE;
-}
-
 /***********************************************************************
  *          WinHttpSetOption (winhttp.@)
  */
diff --git a/dlls/winhttp/request.c b/dlls/winhttp/request.c
index 954f576aa64..14b57cca64d 100644
--- a/dlls/winhttp/request.c
+++ b/dlls/winhttp/request.c
@@ -948,3 +948,31 @@ BOOL WINAPI WinHttpReceiveResponse( HINTERNET hrequest, LPVOID reserved )
     release_object( &request->hdr );
     return ret;
 }
+
+/***********************************************************************
+ *          WinHttpQueryDataAvailable (winhttp.@)
+ */
+BOOL WINAPI WinHttpQueryDataAvailable( HINTERNET hrequest, LPDWORD available )
+{
+    BOOL ret;
+    request_t *request;
+
+    TRACE("%p, %p\n", hrequest, available);
+
+    if (!(request = (request_t *)grab_object( hrequest )))
+    {
+        set_last_error( ERROR_INVALID_HANDLE );
+        return FALSE;
+    }
+    if (request->hdr.type != WINHTTP_HANDLE_TYPE_REQUEST)
+    {
+        release_object( &request->hdr );
+        set_last_error( ERROR_WINHTTP_INCORRECT_HANDLE_TYPE );
+        return FALSE;
+    }
+
+    ret = netconn_query_data_available( &request->netconn, available );
+
+    release_object( &request->hdr );
+    return ret;
+}