1 files changed, 5 insertions, 0 deletions
diff --git a/string.c b/string.c
index c1f14a8525..236980e25b 100644
--- a/string.c
+++ b/string.c
@@ -538,6 +538,11 @@ rb_external_str_new_with_enc(const char *ptr, long len, rb_encoding *eenc)
     VALUE str;
 
     str = rb_tainted_str_new(ptr, len);
+    if (rb_enc_str_coderange(str) != ENC_CODERANGE_7BIT &&
+	eenc == rb_usascii_encoding()) {
+	rb_enc_associate(str, rb_ascii8bit_encoding());
+	return str;
+    }
     rb_enc_associate(str, eenc);
     return rb_str_conv_enc(str, eenc, rb_default_internal_encoding());
 }