diff --git a/csscolorparser.cpp b/csscolorparser.cpp
index 0ce9643..3c226d0 100644
--- a/csscolorparser.cpp
+++ b/csscolorparser.cpp
@@ -33,6 +33,7 @@
 #include <cmath>
 #include <cstring>
 #include <algorithm>
+#include <cctype>
 
 using namespace CSSColorParser;