diff --git a/glx/vndservermapping.c b/glx/vndservermapping.c
index 04788ffbd..e5b9e6b2a 100644
--- a/glx/vndservermapping.c
+++ b/glx/vndservermapping.c
@@ -131,7 +131,6 @@ GlxContextTagInfo *GlxAllocContextTag(ClientPtr client, GlxServerVendor *vendor)
         cl->contextTagCount = newSize;
     }
 
-    assert(index >= 0);
     assert(index < cl->contextTagCount);
     memset(&cl->contextTags[index], 0, sizeof(GlxContextTagInfo));
     cl->contextTags[index].tag = (GLXContextTag) (index + 1);