diff --git a/benchmark/string_casecmp.yml b/benchmark/string_casecmp.yml
index 2354040a04..cc75bc803e 100644
--- a/benchmark/string_casecmp.yml
+++ b/benchmark/string_casecmp.yml
@@ -20,7 +20,9 @@ benchmark:
   casecmp-10: lstr10.casecmp(ustr10)
   casecmp-100: lstr100.casecmp(ustr100)
   casecmp-1000: lstr1000.casecmp(ustr1000)
+  casecmp-1000vs10: lstr1000.casecmp(ustr10)
   casecmp-nonascii1: lnonascii1.casecmp(unonascii1)
   casecmp-nonascii10: lnonascii10.casecmp(unonascii10)
   casecmp-nonascii100: lnonascii100.casecmp(unonascii100)
   casecmp-nonascii1000: lnonascii1000.casecmp(unonascii1000)
+  casecmp-nonascii1000vs10: lnonascii1000.casecmp(unonascii10)
\ No newline at end of file
diff --git a/string.c b/string.c
index fe848d6a4a..96a9f96bd3 100644
--- a/string.c
+++ b/string.c
@@ -4381,9 +4381,9 @@ str_casecmp(VALUE str1, VALUE str2)
             p2 += l2;
         }
     }
-    if (RSTRING_LEN(str1) == RSTRING_LEN(str2)) return INT2FIX(0);
-    if (RSTRING_LEN(str1) > RSTRING_LEN(str2)) return INT2FIX(1);
-    return INT2FIX(-1);
+    if (p1 == p1end && p2 == p2end) return INT2FIX(0);
+    if (p1 == p1end) return INT2FIX(-1);
+    return INT2FIX(1);
 }
 
 /*
diff --git a/test/ruby/test_string.rb b/test/ruby/test_string.rb
index 8fb57bd58e..811785bf7e 100644
--- a/test/ruby/test_string.rb
+++ b/test/ruby/test_string.rb
@@ -2832,9 +2832,12 @@ CODE
   def test_casecmp
     assert_equal(0, S("FoO").casecmp("fOO"))
     assert_equal(1, S("FoO").casecmp("BaR"))
+    assert_equal(-1, S("foo").casecmp("FOOBAR"))
     assert_equal(-1, S("baR").casecmp("FoO"))
     assert_equal(1, S("\u3042B").casecmp("\u3042a"))
     assert_equal(-1, S("foo").casecmp("foo\0"))
+    assert_equal(1,  S("FOOBAR").casecmp("foo"))
+    assert_equal(0, S("foo\0bar").casecmp("FOO\0BAR"))
 
     assert_nil(S("foo").casecmp(:foo))
     assert_nil(S("foo").casecmp(Object.new))
@@ -2842,6 +2845,16 @@ CODE
     o = Object.new
     def o.to_str; "fOO"; end
     assert_equal(0, S("FoO").casecmp(o))
+
+    assert_equal(0, S("#" * 128 + "A" * 256 + "b").casecmp("#" * 128 + "a" * 256 + "B"))
+    assert_equal(0, S("a" * 256 + "B").casecmp("A" * 256 + "b"))
+
+    assert_equal(-1, S("@").casecmp("`"))
+    assert_equal(0, S("hello\u00E9X").casecmp("HELLO\u00E9x"))
+
+    s1 = S("\xff".force_encoding("UTF-8"))
+    s2 = S("\xff".force_encoding("ISO-2022-JP"))
+    assert_nil(s1.casecmp(s2))
   end
 
   def test_casecmp?
@@ -2857,6 +2870,10 @@ CODE
     o = Object.new
     def o.to_str; "fOO"; end
     assert_equal(true, S("FoO").casecmp?(o))
+
+    s1 = S("\xff".force_encoding("UTF-8"))
+    s2 = S("\xff".force_encoding("ISO-2022-JP"))
+    assert_nil(s1.casecmp?(s2))
   end
 
   def test_upcase2