diff --git a/gl_canvas.h b/gl_canvas.h
index ff3fba0..4a15668 100644
--- a/gl_canvas.h
+++ b/gl_canvas.h
@@ -20,6 +20,9 @@
 #include "canvas_base.h"
 #include "region.h"
 
+#ifndef _H__GL_CANVAS
+#define _H__GL_CANVAS
+
 #ifdef __cplusplus
 extern "C" {
 #endif
@@ -42,3 +45,5 @@ void gl_canvas_init();
 #ifdef __cplusplus
 }
 #endif
+
+#endif