diff --git a/src/lib/crypto/MD5.hxx b/src/lib/crypto/MD5.hxx
index 08cd31b81..d8018b6dc 100644
--- a/src/lib/crypto/MD5.hxx
+++ b/src/lib/crypto/MD5.hxx
@@ -35,6 +35,8 @@
 
 #include <array>
 
+#include <stdint.h>
+
 template<typename T> struct ConstBuffer;
 
 void