diff --git a/openscad.h b/openscad.h
index e6add9cc..b6b0b47d 100644
--- a/openscad.h
+++ b/openscad.h
@@ -41,6 +41,7 @@
 #include <errno.h>
 #include <stdlib.h>
 #include <string.h>
+#include <assert.h>
 #include <math.h>
 
 #include <fstream>