diff --git a/include/klein/klein.h b/include/klein/klein.h
index 663c8f1..8295655 100644
--- a/include/klein/klein.h
+++ b/include/klein/klein.h
@@ -3,6 +3,8 @@
 #endif
 #define KLEIN_H
 
+#include <stdint.h>
+
 #ifdef KLEIN_IMPLEMENT
 #include <stdio.h>
 #include <stdlib.h>
@@ -10,9 +12,9 @@
 
 struct klein
 {
-	unsigned long vertex_size;
 	float *vertex, *normals;
-	unsigned char dim;
+	uint64_t vertex_size;
+	uint8_t dim;
 };
 
 /*