diff --git a/lib2geom/src/2geom/utils.h b/lib2geom/src/2geom/utils.h
index 5ab1917..538ef57 100644
--- a/lib2geom/src/2geom/utils.h
+++ b/lib2geom/src/2geom/utils.h
@@ -35,6 +35,7 @@
 
 #include <cmath>
 #include <vector>
+#include <stddef.h>
 
 namespace Geom {