diff --git a/src/utils.c b/src/utils.c
index bc5329d..8f56227 100644
--- a/src/utils.c
+++ b/src/utils.c
@@ -444,6 +444,8 @@
 		/* check for 7-bit ASCII */
 		if (str[i] & 0x80)
 			return false;
+		if (!isprint((int)str[i]))
+			return false;
 		/* check for some explicit reserved control characters */
 		if (strchr(illegal_chars, str[i]))
 			return false;