diff --git a/src/charset.c b/src/charset.c
index 29c587b..cdb9e48 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -960,7 +960,7 @@
 }
 
 /*
- * return TRUE if 'c' is a printable character
+ * Return TRUE if 'c' is a printable character.
  * Assume characters above 0x100 are printable (multi-byte), except for
  * Unicode.
  */
@@ -1717,7 +1717,7 @@
 {
     if (c <= '@')
 	return c;
-    if (c >= 0x80)
+    if (c >= 0x80 || !(cmp_flags & CMP_KEEPASCII))
     {
 	if (enc_utf8)
 	    return utf_toupper(c);
@@ -1741,7 +1741,7 @@
 {
     if (c <= '@')
 	return c;
-    if (c >= 0x80)
+    if (c >= 0x80 || !(cmp_flags & CMP_KEEPASCII))
     {
 	if (enc_utf8)
 	    return utf_tolower(c);