diff --git a/string.c b/string.c
index d724a28f2b..a18eb5777a 100644
--- a/string.c
+++ b/string.c
@@ -1920,16 +1920,12 @@ rb_enc_cr_str_buf_cat(VALUE str, const char *ptr, long len,
     int str_encindex = ENCODING_GET(str);
     int res_encindex;
     int str_cr, res_cr;
-    int ptr_a8 = ptr_encindex == 0;
 
     str_cr = ENC_CODERANGE(str);
 
     if (str_encindex == ptr_encindex) {
         if (str_cr == ENC_CODERANGE_UNKNOWN)
             ptr_cr = ENC_CODERANGE_UNKNOWN;
-	else if (ptr_a8 && str_cr == ENC_CODERANGE_VALID)
-	    /* since str is also ASCII-8BIT, 7bit nor unknown means valid */
-	    ptr_cr = ENC_CODERANGE_VALID;
         else if (ptr_cr == ENC_CODERANGE_UNKNOWN) {
             ptr_cr = coderange_scan(ptr, len, rb_enc_from_index(ptr_encindex));
         }