diff --git a/src/string_func.h b/src/string_func.h
--- a/src/string_func.h
+++ b/src/string_func.h
@@ -257,7 +257,7 @@ char *strndup(const char *s, size_t len)
 #endif /* !_GNU_SOURCE */
 
 /* strcasestr is available for _GNU_SOURCE, BSD and some Apple */
-#if defined(_GNU_SOURCE) || (defined(__BSD_VISIBLE) && __BSD_VISIBLE) || (defined(__APPLE__) && (!defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE))) || _NETBSD_SOURCE
+#if defined(_GNU_SOURCE) || (defined(__BSD_VISIBLE) && __BSD_VISIBLE) || (defined(__APPLE__) && (!defined(_POSIX_C_SOURCE) || defined(_DARWIN_C_SOURCE))) || defined(_NETBSD_SOURCE)
 #	undef DEFINE_STRCASESTR
 #else
 #	define DEFINE_STRCASESTR