diff --git a/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt b/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt
new file mode 100644
index 0000000000..a5cb9b0a09
--- /dev/null
+++ b/tests/baselines/reference/checkTypePredicateForRedundantProperties.errors.txt
@@ -0,0 +1,13 @@
+tests/cases/compiler/checkTypePredicateForRedundantProperties.ts(1,35): error TS2300: Duplicate identifier 'a'.
+tests/cases/compiler/checkTypePredicateForRedundantProperties.ts(1,46): error TS2300: Duplicate identifier 'a'.
+
+
+==== tests/cases/compiler/checkTypePredicateForRedundantProperties.ts (2 errors) ====
+    function addProp2(x: any): x is { a: string; a: string; } {
+                                      ~
+!!! error TS2300: Duplicate identifier 'a'.
+                                                 ~
+!!! error TS2300: Duplicate identifier 'a'.
+        return true;
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/checkTypePredicateForRedundantProperties.js b/tests/baselines/reference/checkTypePredicateForRedundantProperties.js
new file mode 100644
index 0000000000..8f7be2bfbb
--- /dev/null
+++ b/tests/baselines/reference/checkTypePredicateForRedundantProperties.js
@@ -0,0 +1,10 @@
+//// [checkTypePredicateForRedundantProperties.ts]
+function addProp2(x: any): x is { a: string; a: string; } {
+    return true;
+}
+
+
+//// [checkTypePredicateForRedundantProperties.js]
+function addProp2(x) {
+    return true;
+}
diff --git a/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts b/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts
new file mode 100644
index 0000000000..35222f1e9d
--- /dev/null
+++ b/tests/cases/compiler/checkTypePredicateForRedundantProperties.ts
@@ -0,0 +1,3 @@
+function addProp2(x: any): x is { a: string; a: string; } {
+    return true;
+}