1 files changed, 1 insertions, 1 deletions
diff --git a/env.c b/env.c
index 6b6a7d07..ae658bcd 100644
--- a/env.c
+++ b/env.c
@@ -279,7 +279,7 @@ char *visbuf(const char *buf)
 	    *tp++ = '\\'; *tp++ = '\\';
 	    buf++;
 	}
-	else if (isprint(*buf) || *buf == ' ')
+	else if (isprint((unsigned char)*buf) || *buf == ' ')
 	    *tp++ = *buf++;
 	else if (*buf == '\n')
 	{