diff --git a/src/wget.h b/src/wget.h
index ab6270f1..eacf7252 100644
--- a/src/wget.h
+++ b/src/wget.h
@@ -48,8 +48,10 @@ as that of the covered work.  */
 
 /* Disable assertions when debug support is not compiled in. */
 #ifndef ENABLE_DEBUG
+#ifndef NDEBUG
 # define NDEBUG
 #endif
+#endif
 
 /* Is OpenSSL or GNUTLS available? */
 #if defined HAVE_LIBSSL || defined HAVE_LIBSSL32 || defined HAVE_LIBGNUTLS