diff --git a/src/compiler/core.ts b/src/compiler/core.ts
index 1eaab5b1b59..d5caadf079a 100644
--- a/src/compiler/core.ts
+++ b/src/compiler/core.ts
@@ -1272,7 +1272,7 @@ namespace ts {
         if (!left || !right) return false;
         for (const key in left) {
             if (hasOwnProperty.call(left, key)) {
-                if (!hasOwnProperty.call(right, key) === undefined) return false;
+                if (!hasOwnProperty.call(right, key)) return false;
                 if (!equalityComparer(left[key], right[key])) return false;
             }
         }
diff --git a/src/testRunner/tsconfig.json b/src/testRunner/tsconfig.json
index fa7900f1ca3..27dca8296ed 100644
--- a/src/testRunner/tsconfig.json
+++ b/src/testRunner/tsconfig.json
@@ -46,6 +46,7 @@
         "unittests/cancellableLanguageServiceOperations.ts",
         "unittests/commandLineParsing.ts",
         "unittests/compileOnSave.ts",
+        "unittests/compilerCore.ts",
         "unittests/configurationExtension.ts",
         "unittests/convertCompilerOptionsFromJson.ts",
         "unittests/convertToAsyncFunction.ts",
diff --git a/src/testRunner/unittests/compilerCore.ts b/src/testRunner/unittests/compilerCore.ts
new file mode 100644
index 00000000000..27f5cdc0887
--- /dev/null
+++ b/src/testRunner/unittests/compilerCore.ts
@@ -0,0 +1,33 @@
+namespace ts {
+    describe("compilerCore", () => {
+        describe("equalOwnProperties", () => {
+            it("correctly equates objects", () => {
+                assert.isTrue(equalOwnProperties({}, {}));
+                assert.isTrue(equalOwnProperties({ a: 1 }, { a: 1 }));
+                assert.isTrue(equalOwnProperties({ a: 1, b: 2 }, { b: 2, a: 1 }));
+            });
+            it("correctly identifies unmatched objects", () => {
+                assert.isFalse(equalOwnProperties({}, { a: 1 }), "missing left property");
+                assert.isFalse(equalOwnProperties({ a: 1 }, {}), "missing right property");
+                assert.isFalse(equalOwnProperties({ a: 1 }, { a: 2 }), "differing property");
+            });
+            it("correctly identifies undefined vs hasOwnProperty", () => {
+                assert.isFalse(equalOwnProperties({}, { a: undefined }), "missing left property");
+                assert.isFalse(equalOwnProperties({ a: undefined }, {}), "missing right property");
+            });
+            it("truthiness", () => {
+                const trythyTest = (l: any, r: any) => !!l === !!r;
+                assert.isFalse(equalOwnProperties({}, { a: 1 }, trythyTest), "missing left truthy property");
+                assert.isFalse(equalOwnProperties({}, { a: 0 }, trythyTest), "missing left falsey property");
+                assert.isFalse(equalOwnProperties({ a: 1 }, {}, trythyTest), "missing right truthy property");
+                assert.isFalse(equalOwnProperties({ a: 0 }, {}, trythyTest), "missing right falsey property");
+                assert.isTrue(equalOwnProperties({ a: 1 }, { a: "foo" }, trythyTest), "valid equality");
+            });
+            it("all equal", () => {
+                assert.isFalse(equalOwnProperties({}, { a: 1 }, () => true), "missing left property");
+                assert.isFalse(equalOwnProperties({ a: 1 }, {}, () => true), "missing right property");
+                assert.isTrue(equalOwnProperties({ a: 1 }, { a: 2 }, () => true), "valid equality");
+            });
+        });
+    });
+}