diff --git a/sys/winnt/winnt.c b/sys/winnt/winnt.c
index 09ee0c9b4..f34a68397 100644
--- a/sys/winnt/winnt.c
+++ b/sys/winnt/winnt.c
@@ -726,9 +726,19 @@ nt_assert_failed(expression, filepath, line)
 {
     const char * filename;
 
-    /* get file name from path */
     filename = strrchr(filepath, '\\');
     filename = (filename == NULL ? filepath : filename + 1);
+
+    if (IsDebuggerPresent()) {
+        char message[BUFSIZ];
+        snprintf(message, sizeof(message), 
+            "nhassert(%s) failed in file '%s' at line %d",
+            expression, filename, line);
+        OutputDebugStringA(message);
+        DebugBreak();
+    }
+
+    /* get file name from path */
     impossible("nhassert(%s) failed in file '%s' at line %d",
                 expression, filename, line);
 }