diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index a459db40e1b..814a0032104 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -3206,7 +3206,9 @@ namespace ts {
             // Use the type of the initializer expression if one is present
             if (declaration.initializer) {
                 const type = checkDeclarationInitializer(declaration);
-                const isOptional = declaration.questionToken || (declaration.initializer && declaration.kind === SyntaxKind.Parameter);
+                // initialized parameters (but not parameter properties) are optional
+                const isOptional = declaration.questionToken ||
+                    (declaration.kind === SyntaxKind.Parameter && !(getModifierFlags(declaration) & ModifierFlags.ParameterPropertyModifier));
                 return addOptionality(type, isOptional && includeOptionality);
             }
 
diff --git a/tests/baselines/reference/optionalMethods.js b/tests/baselines/reference/optionalMethods.js
index 953ebb527a5..28ed0bcd76e 100644
--- a/tests/baselines/reference/optionalMethods.js
+++ b/tests/baselines/reference/optionalMethods.js
@@ -128,11 +128,11 @@ interface Foo {
 declare function test1(x: Foo): void;
 declare class Bar {
     d: number;
-    e: number | undefined;
+    e: number;
     a: number;
     b?: number;
     c?: number | undefined;
-    constructor(d?: number, e?: number | undefined);
+    constructor(d?: number, e?: number);
     f(): number;
     g?(): number;
     h?(): number;
diff --git a/tests/baselines/reference/optionalMethods.types b/tests/baselines/reference/optionalMethods.types
index cf86f8b6bcf..cf545eda509 100644
--- a/tests/baselines/reference/optionalMethods.types
+++ b/tests/baselines/reference/optionalMethods.types
@@ -87,7 +87,7 @@ class Bar {
 
     constructor(public d?: number, public e = 10) {}
 >d : number | undefined
->e : number | undefined
+>e : number
 >10 : 10
 
     f() {
@@ -133,9 +133,9 @@ function test2(x: Bar) {
 >d : number | undefined
 
     x.e;
->x.e : number | undefined
+>x.e : number
 >x : Bar
->e : number | undefined
+>e : number
 
     x.f;
 >x.f : () => number