diff --git a/cplusplus/p0004.cpp b/cplusplus/p0004.cpp
index de5dd984..e5714582 100644
--- a/cplusplus/p0004.cpp
+++ b/cplusplus/p0004.cpp
@@ -13,6 +13,7 @@ Find the largest palindrome made from the product of two 3-digit numbers.
 #ifndef EULER_P0004
 #define EULER_P0004
 #include <algorithm>
+#include <cstdio>
 #include <iostream>
 
 unsigned int p0004() {