diff --git a/include/sudo_compat.h b/include/sudo_compat.h
index 89fcac5e1..9d100a44f 100644
--- a/include/sudo_compat.h
+++ b/include/sudo_compat.h
@@ -312,7 +312,7 @@ extern int errno;
 #endif
 
 /* For sig2str() */
-#if defined(HAVE_DECL_SIG2STR_MAX) && !HAVE_DECL_SIG2STR_MAX
+#if !defined(HAVE_DECL_SIG2STR_MAX) || !HAVE_DECL_SIG2STR_MAX
 # define SIG2STR_MAX 32
 #endif