diff --git a/LifeAPI.h b/LifeAPI.h
index 548afec..f5a2f96 100644
--- a/LifeAPI.h
+++ b/LifeAPI.h
@@ -19,9 +19,9 @@
 #define YES 1
 #define NO 0
 
-#ifdef __MSC_VER
+#ifdef _MSC_VER
 	#include <intrin.h>
-	#define __builtin_popcount __popcnt64
+	#define __builtin_popcountll __popcnt64
 #endif
 
 enum CopyType { COPY, OR, XOR, AND };
@@ -1919,4 +1919,4 @@ int IsInside(LifeState* state, LifeBox* box)
 int IsInside(LifeBox* box)
 {
 	return IsInside(GlobalState, box);
-}
\ No newline at end of file
+}