diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 2411cce31b..ac1135788c 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -5241,6 +5241,7 @@ namespace ts {
                 let hasThisParameter: boolean;
                 const iife = getImmediatelyInvokedFunctionExpression(declaration);
                 const isJSConstructSignature = isJSDocConstructSignature(declaration);
+                const isUntypedSignatureInJSFile = !iife && !isJSConstructSignature && isInJavaScriptFile(declaration) && !hasJSDocParameterTags(declaration);
 
                 // If this is a JSDoc construct signature, then skip the first parameter in the
                 // parameter list.  The first parameter represents the return type of the construct
@@ -5269,7 +5270,8 @@ namespace ts {
                     // Record a new minimum argument count if this is not an optional parameter
                     const isOptionalParameter = param.initializer || param.questionToken || param.dotDotDotToken ||
                         iife && parameters.length > iife.arguments.length && !param.type ||
-                        isJSDocOptionalParameter(param);
+                        isJSDocOptionalParameter(param) ||
+                        isUntypedSignatureInJSFile;
                     if (!isOptionalParameter) {
                         minArgumentCount = parameters.length;
                     }
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 91cd6a89b8..39d53a9a9c 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -1518,6 +1518,11 @@ namespace ts {
         return map(getJSDocs(node), doc => doc.comment);
     }
 
+    export function hasJSDocParameterTags(node: FunctionLikeDeclaration | SignatureDeclaration) {
+        const parameterTags = getJSDocTags(node, SyntaxKind.JSDocParameterTag);
+        return parameterTags && parameterTags.length > 0;
+    }
+
     function getJSDocTags(node: Node, kind: SyntaxKind): JSDocTag[] {
         const docs = getJSDocs(node);
         if (docs) {
diff --git a/tests/baselines/reference/jsFileFunctionParametersAsOptional.symbols b/tests/baselines/reference/jsFileFunctionParametersAsOptional.symbols
new file mode 100644
index 0000000000..040b910f37
--- /dev/null
+++ b/tests/baselines/reference/jsFileFunctionParametersAsOptional.symbols
@@ -0,0 +1,22 @@
+=== tests/cases/compiler/foo.js ===
+
+function f(a, b, c) { }
+>f : Symbol(f, Decl(foo.js, 0, 0))
+>a : Symbol(a, Decl(foo.js, 1, 11))
+>b : Symbol(b, Decl(foo.js, 1, 13))
+>c : Symbol(c, Decl(foo.js, 1, 16))
+
+
+=== tests/cases/compiler/bar.ts ===
+f();
+>f : Symbol(f, Decl(foo.js, 0, 0))
+
+f(1);
+>f : Symbol(f, Decl(foo.js, 0, 0))
+
+f(1, 2);
+>f : Symbol(f, Decl(foo.js, 0, 0))
+
+f(1, 2, 3);
+>f : Symbol(f, Decl(foo.js, 0, 0))
+
diff --git a/tests/baselines/reference/jsFileFunctionParametersAsOptional.types b/tests/baselines/reference/jsFileFunctionParametersAsOptional.types
new file mode 100644
index 0000000000..d6d8f9b04a
--- /dev/null
+++ b/tests/baselines/reference/jsFileFunctionParametersAsOptional.types
@@ -0,0 +1,32 @@
+=== tests/cases/compiler/foo.js ===
+
+function f(a, b, c) { }
+>f : (a: any, b: any, c: any) => void
+>a : any
+>b : any
+>c : any
+
+
+=== tests/cases/compiler/bar.ts ===
+f();
+>f() : void
+>f : (a: any, b: any, c: any) => void
+
+f(1);
+>f(1) : void
+>f : (a: any, b: any, c: any) => void
+>1 : 1
+
+f(1, 2);
+>f(1, 2) : void
+>f : (a: any, b: any, c: any) => void
+>1 : 1
+>2 : 2
+
+f(1, 2, 3);
+>f(1, 2, 3) : void
+>f : (a: any, b: any, c: any) => void
+>1 : 1
+>2 : 2
+>3 : 3
+
diff --git a/tests/baselines/reference/jsFileFunctionParametersAsOptional2.errors.txt b/tests/baselines/reference/jsFileFunctionParametersAsOptional2.errors.txt
new file mode 100644
index 0000000000..26ada935ee
--- /dev/null
+++ b/tests/baselines/reference/jsFileFunctionParametersAsOptional2.errors.txt
@@ -0,0 +1,28 @@
+tests/cases/compiler/bar.ts(1,1): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/compiler/bar.ts(2,1): error TS2346: Supplied parameters do not match any signature of call target.
+tests/cases/compiler/bar.ts(3,1): error TS2346: Supplied parameters do not match any signature of call target.
+
+
+==== tests/cases/compiler/foo.js (0 errors) ====
+    
+    /**
+     * @param a
+     * @param b
+     * @param c
+     */
+    function f(a, b, c) { }
+    
+    
+==== tests/cases/compiler/bar.ts (3 errors) ====
+    f(); // Error
+    ~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    f(1); // Error
+    ~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    f(1, 2); // Error
+    ~~~~~~~
+!!! error TS2346: Supplied parameters do not match any signature of call target.
+    
+    f(1, 2, 3); // OK
+    
\ No newline at end of file
diff --git a/tests/cases/compiler/jsFileFunctionParametersAsOptional.ts b/tests/cases/compiler/jsFileFunctionParametersAsOptional.ts
new file mode 100644
index 0000000000..f2673f310b
--- /dev/null
+++ b/tests/cases/compiler/jsFileFunctionParametersAsOptional.ts
@@ -0,0 +1,12 @@
+// @allowJs: true
+// @noEmit: true
+
+// @filename: foo.js
+function f(a, b, c) { }
+
+
+// @filename: bar.ts
+f();
+f(1);
+f(1, 2);
+f(1, 2, 3);
diff --git a/tests/cases/compiler/jsFileFunctionParametersAsOptional2.ts b/tests/cases/compiler/jsFileFunctionParametersAsOptional2.ts
new file mode 100644
index 0000000000..01aebb2971
--- /dev/null
+++ b/tests/cases/compiler/jsFileFunctionParametersAsOptional2.ts
@@ -0,0 +1,18 @@
+// @allowJs: true
+// @noEmit: true
+
+// @filename: foo.js
+/**
+ * @param a
+ * @param b
+ * @param c
+ */
+function f(a, b, c) { }
+
+
+// @filename: bar.ts
+f(); // Error
+f(1); // Error
+f(1, 2); // Error
+
+f(1, 2, 3); // OK