diff --git a/src/util/parser.c b/src/util/parser.c
index b13e266a6..0fbde6769 100644
--- a/src/util/parser.c
+++ b/src/util/parser.c
@@ -6,6 +6,7 @@
 
 #include <assert.h>
 #include <stdlib.h>
+#include <ctype.h>
 #include <wctype.h>
 #include <memory.h>