diff --git a/reactos/win32ss/gdi/eng/semaphor.c b/reactos/win32ss/gdi/eng/semaphor.c
index 48ee574f24a..fa72ea3fa7d 100644
--- a/reactos/win32ss/gdi/eng/semaphor.c
+++ b/reactos/win32ss/gdi/eng/semaphor.c
@@ -68,7 +68,14 @@ EngReleaseSemaphore(
 {
     // www.osr.com/ddk/graphics/gdifncs_5u3r.htm
     PTHREADINFO W32Thread;
-    ASSERT(hsem);
+
+    /* On Windows a NULL hsem is ignored */
+    if (hsem == NULL)
+    {
+        DPRINT1("EngReleaseSemaphore called with hsem == NULL!\n");
+        return;
+    }
+
     W32Thread = PsGetThreadWin32Thread(PsGetCurrentThread());
     if (W32Thread) --W32Thread->dwEngAcquireCount;
     ExReleaseResourceAndLeaveCriticalRegion((PERESOURCE)hsem);