diff --git a/src/core/bitmath_func.hpp b/src/core/bitmath_func.hpp
index fdcb310b06..a40c7dba6e 100644
--- a/src/core/bitmath_func.hpp
+++ b/src/core/bitmath_func.hpp
@@ -365,7 +365,7 @@ static inline T ROR(const T x, const uint8 n)
 	 * (since it will use hardware swapping if available).
 	 * Even though they should return uint16 and uint32, we get
 	 * warnings if we don't cast those (why?) */
-	#define BSWAP64(x) ((uint32)CFSwapInt64(x))
+	#define BSWAP64(x) ((uint64)CFSwapInt64(x))
 	#define BSWAP32(x) ((uint32)CFSwapInt32(x))
 	#define BSWAP16(x) ((uint16)CFSwapInt16(x))
 #elif defined(_MSC_VER)