diff --git a/.gitignore b/.gitignore
index d321659..57c96f5 100644
--- a/.gitignore
+++ b/.gitignore
@@ -6,4 +6,5 @@ atlassian-ide-plugin.xml
 npm-debug.log
 report/
 node_modules/
-out/
\ No newline at end of file
+out/
+package-lock.json
diff --git a/sorted-array.js b/sorted-array.js
index d2311a4..a75d731 100644
--- a/sorted-array.js
+++ b/sorted-array.js
@@ -108,8 +108,7 @@ function searchForInsertionIndex(array, value, compare) {
     if (index < 0) {
         return -index - 1;
     } else {
-        var last = array.length - 1;
-        while (index < last && compare(value, array[index + 1]) === 0) {
+        while (index < array.length && compare(value, array[index]) === 0) {
             index++;
         }
         return index;
diff --git a/test/spec/sorted-array-spec.js b/test/spec/sorted-array-spec.js
index b87c467..c987999 100644
--- a/test/spec/sorted-array-spec.js
+++ b/test/spec/sorted-array-spec.js
@@ -37,6 +37,30 @@ describe("SortedArray-spec", function () {
         });
     });
 
+    describe("stable", function () {
+        let collection;
+
+        beforeEach(() => {
+            collection = new SortedArray([{k:0, v:"a"}, {k:1, v:"b"}], null, function(a, b) {
+                return a.k - b.k;
+            });
+        });
+
+        it("should add at the end of sequence", function () {
+            collection.add({k:1, v:"q"});
+            expect(collection.toArray()[0].v).toBe("a")
+            expect(collection.toArray()[1].v).toBe("b")
+            expect(collection.toArray()[2].v).toBe("q")
+        });
+
+        it("should add at the end of subsequence", function () {
+            collection.add({k:0, v:"q"});
+            expect(collection.toArray()[0].v).toBe("a")
+            expect(collection.toArray()[1].v).toBe("q")
+            expect(collection.toArray()[2].v).toBe("b")
+        });
+    })
+
     describe("incomparable values", function () {
         function customEquals(one, two) {
             return one.id === two.id;