diff --git a/vrclient_x64/vrclient_defs.h b/vrclient_x64/vrclient_defs.h
index 35e8ce8d..e89c2024 100644
--- a/vrclient_x64/vrclient_defs.h
+++ b/vrclient_x64/vrclient_defs.h
@@ -1,5 +1,7 @@
 #ifndef __cplusplus
+#ifndef bool
 typedef char bool; /* 1 byte on modern visual studio c++ */
+#endif
 
 /* enums */
 typedef int