Index: generic/nsfError.c
===================================================================
diff -u -r8d2096ecf0bbe174618e0f3b369c51e9d403d2c4 -r2a16d792aa36cb6bfe4c212ae34aa43bb7c1013d
--- generic/nsfError.c	(.../nsfError.c)	(revision 8d2096ecf0bbe174618e0f3b369c51e9d403d2c4)
+++ generic/nsfError.c	(.../nsfError.c)	(revision 2a16d792aa36cb6bfe4c212ae34aa43bb7c1013d)
@@ -156,11 +156,12 @@
     failure = (result == -1 || result >= avail);
 #endif
 
-    assert(failure == 0);
-    
+#if defined(NDEBUG)
     if (unlikely(failure != 0)) {
       fprintf(stderr, "writing string-formatting output to a dynamic Tcl string failed\n");
     }
+#endif
+    assert(failure == 0);
   }
 }