diff --git a/simgear/canvas/elements/CanvasPath.cxx b/simgear/canvas/elements/CanvasPath.cxx
index 9197d21f..653930cf 100644
--- a/simgear/canvas/elements/CanvasPath.cxx
+++ b/simgear/canvas/elements/CanvasPath.cxx
@@ -25,6 +25,7 @@
 
 #include <vg/openvg.h>
 #include <cassert>
+#include <cctype>
 
 namespace simgear
 {