diff --git a/src/LinearMath/btMatrixX.h b/src/LinearMath/btMatrixX.h
index a3e46b2d4..42caed42e 100644
--- a/src/LinearMath/btMatrixX.h
+++ b/src/LinearMath/btMatrixX.h
@@ -19,6 +19,7 @@ subject to the following restrictions:
 
 #include "LinearMath/btQuickprof.h"
 #include "LinearMath/btAlignedObjectArray.h"
+#include <stdio.h>
 
 //#define BT_DEBUG_OSTREAM
 #ifdef BT_DEBUG_OSTREAM