diff --git a/gcc/testsuite/gcc.dg/cpp/defined_trad.c b/gcc/testsuite/gcc.dg/cpp/defined_trad.c
index 5f5a8133fe7..1902b061b84 100644
--- a/gcc/testsuite/gcc.dg/cpp/defined_trad.c
+++ b/gcc/testsuite/gcc.dg/cpp/defined_trad.c
@@ -5,8 +5,13 @@
 
 /* Tests tradcpp0 with defined.  */
 
-/*  Source: Neil Booth, 11 Dec 2000.  */
+/* Source: Glibc, 11 Dec 2000.  */
 
 #if defined REGPARMS
 #error REGPARMS should not be defined
 #endif
+
+#define REGPARMS 1
+#if !defined REGPARMS
+#error REGPARMS should be defined
+#endif