diff --git a/src/p_unix.cpp b/src/p_unix.cpp
index e8db891f..d6bb33ff 100644
--- a/src/p_unix.cpp
+++ b/src/p_unix.cpp
@@ -57,6 +57,11 @@ PackUnix::PackUnix(InputFile *f) :
 }
 
 
+#ifndef S_IXUSR  //{ MSVC lacks this
+#define S_IXUSR __S_IEXEC
+#define __S_IEXEC 0100  /* Execute by owner.  */
+#endif  //}
+
 // common part of canPack(), enhanced by subclasses
 bool PackUnix::canPack()
 {