diff --git a/libImaging/QuantTypes.h b/libImaging/QuantTypes.h
index 8f113b082..411485498 100644
--- a/libImaging/QuantTypes.h
+++ b/libImaging/QuantTypes.h
@@ -14,6 +14,7 @@
 
 #ifdef _MSC_VER
 typedef unsigned __int32 uint32_t;
+typedef unsigned __int64 uint64_t;
 #else
 #include <stdint.h>
 #endif