diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index ab50ca652d..9393b7b6d1 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -4401,7 +4401,7 @@ namespace ts {
             return result;
         }
 
-        function isOptionalParameter(node: ParameterDeclaration) {
+        function isJSDocOptionalParameter(node: ParameterDeclaration) {
             if (node.flags & NodeFlags.JavaScriptFile) {
                 if (node.type && node.type.kind === SyntaxKind.JSDocOptionalType) {
                     return true;
@@ -4418,8 +4418,10 @@ namespace ts {
                     }
                 }
             }
+        }
 
-            if (hasQuestionToken(node)) {
+        function isOptionalParameter(node: ParameterDeclaration) {
+            if (hasQuestionToken(node) || isJSDocOptionalParameter(node)) {
                 return true;
             }
 
@@ -4486,7 +4488,7 @@ namespace ts {
                         hasStringLiterals = true;
                     }
 
-                    if (param.initializer || param.questionToken || param.dotDotDotToken) {
+                    if (param.initializer || param.questionToken || param.dotDotDotToken || isJSDocOptionalParameter(param)) {
                         if (minArgumentCount < 0) {
                             minArgumentCount = i - (hasThisParameter ? 1 : 0);
                         }
diff --git a/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.js b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.js
new file mode 100644
index 0000000000..b3d61a9f59
--- /dev/null
+++ b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.js
@@ -0,0 +1,32 @@
+//// [jsDocOptionality.js]
+function MyClass() {
+  this.prop = null;
+}
+/**
+ * @param  {string} required
+ * @param  {string} [notRequired]
+ * @returns {MyClass}
+ */
+MyClass.prototype.optionalParam = function(required, notRequired) {
+    return this;
+};
+let pInst = new MyClass();
+let c1 = pInst.optionalParam('hello')
+let c2 = pInst.optionalParam('hello', null)
+
+
+//// [out_1.js]
+function MyClass() {
+    this.prop = null;
+}
+/**
+ * @param  {string} required
+ * @param  {string} [notRequired]
+ * @returns {MyClass}
+ */
+MyClass.prototype.optionalParam = function (required, notRequired) {
+    return this;
+};
+var pInst = new MyClass();
+var c1 = pInst.optionalParam('hello');
+var c2 = pInst.optionalParam('hello', null);
diff --git a/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.symbols b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.symbols
new file mode 100644
index 0000000000..5ea2756598
--- /dev/null
+++ b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.symbols
@@ -0,0 +1,38 @@
+=== tests/cases/compiler/jsDocOptionality.js ===
+function MyClass() {
+>MyClass : Symbol(MyClass, Decl(jsDocOptionality.js, 0, 0))
+
+  this.prop = null;
+>prop : Symbol(MyClass.prop, Decl(jsDocOptionality.js, 0, 20))
+}
+/**
+ * @param  {string} required
+ * @param  {string} [notRequired]
+ * @returns {MyClass}
+ */
+MyClass.prototype.optionalParam = function(required, notRequired) {
+>MyClass.prototype : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+>MyClass : Symbol(MyClass, Decl(jsDocOptionality.js, 0, 0))
+>prototype : Symbol(Function.prototype, Decl(lib.d.ts, --, --))
+>optionalParam : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+>required : Symbol(required, Decl(jsDocOptionality.js, 8, 43))
+>notRequired : Symbol(notRequired, Decl(jsDocOptionality.js, 8, 52))
+
+    return this;
+};
+let pInst = new MyClass();
+>pInst : Symbol(pInst, Decl(jsDocOptionality.js, 11, 3))
+>MyClass : Symbol(MyClass, Decl(jsDocOptionality.js, 0, 0))
+
+let c1 = pInst.optionalParam('hello')
+>c1 : Symbol(c1, Decl(jsDocOptionality.js, 12, 3))
+>pInst.optionalParam : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+>pInst : Symbol(pInst, Decl(jsDocOptionality.js, 11, 3))
+>optionalParam : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+
+let c2 = pInst.optionalParam('hello', null)
+>c2 : Symbol(c2, Decl(jsDocOptionality.js, 13, 3))
+>pInst.optionalParam : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+>pInst : Symbol(pInst, Decl(jsDocOptionality.js, 11, 3))
+>optionalParam : Symbol(MyClass.optionalParam, Decl(jsDocOptionality.js, 2, 1))
+
diff --git a/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.types b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.types
new file mode 100644
index 0000000000..2dcaa37b94
--- /dev/null
+++ b/tests/baselines/reference/signaturesUseJSDocForOptionalParameters.types
@@ -0,0 +1,53 @@
+=== tests/cases/compiler/jsDocOptionality.js ===
+function MyClass() {
+>MyClass : () => void
+
+  this.prop = null;
+>this.prop = null : null
+>this.prop : any
+>this : any
+>prop : any
+>null : null
+}
+/**
+ * @param  {string} required
+ * @param  {string} [notRequired]
+ * @returns {MyClass}
+ */
+MyClass.prototype.optionalParam = function(required, notRequired) {
+>MyClass.prototype.optionalParam = function(required, notRequired) {    return this;} : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>MyClass.prototype.optionalParam : any
+>MyClass.prototype : any
+>MyClass : () => void
+>prototype : any
+>optionalParam : any
+>function(required, notRequired) {    return this;} : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>required : string
+>notRequired : string
+
+    return this;
+>this : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+
+};
+let pInst = new MyClass();
+>pInst : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>new MyClass() : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>MyClass : () => void
+
+let c1 = pInst.optionalParam('hello')
+>c1 : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>pInst.optionalParam('hello') : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>pInst.optionalParam : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>pInst : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>optionalParam : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>'hello' : string
+
+let c2 = pInst.optionalParam('hello', null)
+>c2 : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>pInst.optionalParam('hello', null) : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>pInst.optionalParam : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>pInst : { prop: null; optionalParam: (required: string, notRequired?: string) => { prop: null; optionalParam: any; }; }
+>optionalParam : (required: string, notRequired?: string) => { prop: null; optionalParam: any; }
+>'hello' : string
+>null : null
+
diff --git a/tests/cases/compiler/signaturesUseJSDocForOptionalParameters.ts b/tests/cases/compiler/signaturesUseJSDocForOptionalParameters.ts
new file mode 100644
index 0000000000..a6f9c9fb39
--- /dev/null
+++ b/tests/cases/compiler/signaturesUseJSDocForOptionalParameters.ts
@@ -0,0 +1,17 @@
+// @allowJs: true
+// @out: out_1.js
+// @filename: jsDocOptionality.js
+function MyClass() {
+  this.prop = null;
+}
+/**
+ * @param  {string} required
+ * @param  {string} [notRequired]
+ * @returns {MyClass}
+ */
+MyClass.prototype.optionalParam = function(required, notRequired) {
+    return this;
+};
+let pInst = new MyClass();
+let c1 = pInst.optionalParam('hello')
+let c2 = pInst.optionalParam('hello', null)