diff --git a/jerry-core/jerry-port.c b/jerry-core/jerry-port.c
index 4812410927..3a8cb8b3d1 100644
--- a/jerry-core/jerry-port.c
+++ b/jerry-core/jerry-port.c
@@ -50,5 +50,5 @@ int jerry_port_errormsg (const char *format, /**< format string */
  */
 int jerry_port_putchar (int c) /**< character to put */
 {
-  return putchar (c);
+  return putchar ((unsigned char) c);
 } /* jerry_port_putchar */