diff --git a/makeint.h b/makeint.h
index da267cb2..eefcde9b 100644
--- a/makeint.h
+++ b/makeint.h
@@ -351,7 +351,7 @@ char *strsignal (int signum);
 # define pipe(_p)        _pipe((_p), 512, O_BINARY)
 # define kill(_pid,_sig) w32_kill((_pid),(_sig))
 /* MSVC doesn't have ftruncate.  */
-# ifdef _MSC_VER
+# if defined(_MSC_VER) || defined(__WATCOMC__)
 #  define ftruncate(_fd,_len) _chsize(_fd,_len)
 # endif
 /* MinGW64 doesn't have _S_ISDIR.  */