diff --git a/packages/ember-runtime/lib/compare.js b/packages/ember-runtime/lib/compare.js
index ac668e95935..a32dc89b82d 100644
--- a/packages/ember-runtime/lib/compare.js
+++ b/packages/ember-runtime/lib/compare.js
@@ -109,7 +109,18 @@ export default function compare(v, w) {
       return spaceship(v, w);
 
     case 'string':
-      return spaceship(v.localeCompare(w), 0);
+      // We are comparing Strings using operators instead of `String#localeCompare`
+      // because of unexpected behavior for certain edge cases.
+      // For example `'Z'.localeCompare('a')` returns `1`.
+      //
+      // See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/localeCompare#Description
+      if (v < w) {
+        return -1;
+      } else if (v === w) {
+        return 0;
+      }
+
+      return 1;
 
     case 'array':
       var vLen = v.length;
diff --git a/packages/ember-runtime/tests/core/compare_test.js b/packages/ember-runtime/tests/core/compare_test.js
index 0f8a6bc4200..f1ba17f2d89 100644
--- a/packages/ember-runtime/tests/core/compare_test.js
+++ b/packages/ember-runtime/tests/core/compare_test.js
@@ -74,4 +74,8 @@ QUnit.test('comparables should return values in the range of -1, 0, 1', function
   equal(compare('a', negOne), 1, 'Second item comparable - returns -1 (negated)');
   equal(compare('b', zero), 0, 'Second item comparable - returns  0 (negated)');
   equal(compare('c', one), -1, 'Second item comparable - returns  1 (negated)');
+
+  equal(compare('A', 'Z'), -1, `'A' < 'Z' returns -1`);
+  equal(compare('Z', 'a'), -1, `'Z' < 'a' returns -1`);
+  equal(compare('a', 'z'), -1, `'a' < 'z' returns -1`);
 });