diff --git a/hash.c b/hash.c
index 769af0df7d..71bbfea4a0 100644
--- a/hash.c
+++ b/hash.c
@@ -6343,13 +6343,29 @@ env_invert(VALUE _)
     return rb_hash_invert(env_to_hash());
 }
 
+static void
+keylist_delete(VALUE keys, VALUE key)
+{
+    long keylen, elen;
+    const char *keyptr, *eptr;
+    RSTRING_GETMEM(key, keyptr, keylen);
+    for (long i=0; i<RARRAY_LEN(keys); i++) {
+        VALUE e = RARRAY_AREF(keys, i);
+        RSTRING_GETMEM(e, eptr, elen);
+        if (elen != keylen) continue;
+        if (!ENVNMATCH(keyptr, eptr, elen)) continue;
+        rb_ary_delete_at(keys, i);
+        return;
+    }
+}
+
 static int
 env_replace_i(VALUE key, VALUE val, VALUE keys)
 {
+    env_name(key);
     env_aset(key, val);
-    if (rb_ary_includes(keys, key)) {
-	rb_ary_delete(keys, key);
-    }
+
+    keylist_delete(keys, key);
     return ST_CONTINUE;
 }
 
diff --git a/test/ruby/test_env.rb b/test/ruby/test_env.rb
index f93cd503d8..02cd3b8502 100644
--- a/test/ruby/test_env.rb
+++ b/test/ruby/test_env.rb
@@ -433,6 +433,8 @@ class TestEnv < Test::Unit::TestCase
     ENV["foo"] = "xxx"
     ENV.replace({"foo"=>"bar", "baz"=>"qux"})
     check(ENV.to_hash.to_a, [%w(foo bar), %w(baz qux)])
+    ENV.replace({"Foo"=>"Bar", "Baz"=>"Qux"})
+    check(ENV.to_hash.to_a, [%w(Foo Bar), %w(Baz Qux)])
   end
 
   def test_update