diff --git a/compiler-rt/BlocksRuntime/Block_private.h b/compiler-rt/BlocksRuntime/Block_private.h
index 7b069d8997a7..8ae821815ebe 100644
--- a/compiler-rt/BlocksRuntime/Block_private.h
+++ b/compiler-rt/BlocksRuntime/Block_private.h
@@ -33,7 +33,14 @@
 #   endif
 #endif
 
+#ifndef _MSC_VER
 #include <stdbool.h>
+#else
+/* MSVC doesn't have <stdbool.h>. Compensate. */
+typedef char bool;
+#define true (bool)1
+#define false (bool)0
+#endif
 
 #if defined(__cplusplus)
 extern "C" {
diff --git a/compiler-rt/BlocksRuntime/runtime.c b/compiler-rt/BlocksRuntime/runtime.c
index dae06321f6e7..a059c2234df1 100644
--- a/compiler-rt/BlocksRuntime/runtime.c
+++ b/compiler-rt/BlocksRuntime/runtime.c
@@ -27,7 +27,6 @@
 #include <stdlib.h>
 #include <string.h>
 #include <stdint.h>
-#include <stdbool.h>
 
 #include "config.h"
 
@@ -45,7 +44,7 @@
 #include <libkern/OSAtomic.h>
 #endif /* HAVE_LIBKERN_OSATOMIC_H */
 
-#elif defined(__WIN32__)
+#elif defined(__WIN32__) || defined(_WIN32)
 #define _CRT_SECURE_NO_WARNINGS 1
 #include <windows.h>