diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 28082914256a3..f35a53ce368e4 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -13552,9 +13552,6 @@ namespace ts {
                 }
             }
 
-            // when checking exported function declarations across modules check only duplicate implementations
-            // names and consistency of modifiers are verified when we check local symbol
-            const isExportSymbolInsideModule = symbol.parent && symbol.parent.flags & SymbolFlags.Module;
             let duplicateFunctionDeclaration = false;
             let multipleConstructorImplementation = false;
             for (const current of declarations) {
@@ -13587,7 +13584,7 @@ namespace ts {
                             duplicateFunctionDeclaration = true;
                         }
                     }
-                    else if (!isExportSymbolInsideModule && previousDeclaration && previousDeclaration.parent === node.parent && previousDeclaration.end !== node.pos) {
+                    else if (previousDeclaration && previousDeclaration.parent === node.parent && previousDeclaration.end !== node.pos) {
                         reportImplementationExpectedError(previousDeclaration);
                     }
 
@@ -13621,7 +13618,7 @@ namespace ts {
             }
 
             // Abstract methods can't have an implementation -- in particular, they don't need one.
-            if (!isExportSymbolInsideModule && lastSeenNonAmbientDeclaration && !lastSeenNonAmbientDeclaration.body &&
+            if (lastSeenNonAmbientDeclaration && !lastSeenNonAmbientDeclaration.body &&
                 !(lastSeenNonAmbientDeclaration.flags & NodeFlags.Abstract) && !lastSeenNonAmbientDeclaration.questionToken) {
                 reportImplementationExpectedError(lastSeenNonAmbientDeclaration);
             }
diff --git a/tests/baselines/reference/missingFunctionImplementation.errors.txt b/tests/baselines/reference/missingFunctionImplementation.errors.txt
new file mode 100644
index 0000000000000..4cf58d97d4909
--- /dev/null
+++ b/tests/baselines/reference/missingFunctionImplementation.errors.txt
@@ -0,0 +1,140 @@
+tests/cases/compiler/missingFunctionImplementation.ts(3,3): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(8,3): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(16,3): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(22,10): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(28,10): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(33,10): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(41,10): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(48,10): error TS2300: Duplicate identifier 'm'.
+tests/cases/compiler/missingFunctionImplementation.ts(49,10): error TS2300: Duplicate identifier 'm'.
+tests/cases/compiler/missingFunctionImplementation.ts(49,10): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(52,19): error TS2300: Duplicate identifier 'm'.
+tests/cases/compiler/missingFunctionImplementation.ts(57,10): error TS2300: Duplicate identifier 'm'.
+tests/cases/compiler/missingFunctionImplementation.ts(60,19): error TS2300: Duplicate identifier 'm'.
+tests/cases/compiler/missingFunctionImplementation.ts(60,19): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(65,19): error TS2391: Function implementation is missing or not immediately following the declaration.
+tests/cases/compiler/missingFunctionImplementation.ts(73,19): error TS2393: Duplicate function implementation.
+tests/cases/compiler/missingFunctionImplementation.ts(74,19): error TS2393: Duplicate function implementation.
+tests/cases/compiler/missingFunctionImplementation.ts(75,19): error TS2393: Duplicate function implementation.
+tests/cases/compiler/missingFunctionImplementation.ts(78,19): error TS2393: Duplicate function implementation.
+
+
+==== tests/cases/compiler/missingFunctionImplementation.ts (19 errors) ====
+    
+    export class C1 {
+      m(): void;
+      ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    
+    // merged with a namespace
+    export class C2 {
+      m(): void;
+      ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    export namespace C2 { }
+    
+    
+    // merged with a namespace, multiple overloads
+    class C3 {
+      m(a, b);
+      m(a);
+      ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    namespace C3 { }
+    
+    // static methods, multiple overloads
+    class C4 {
+      static m(a): void;
+             ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    
+    // static methods, multiple overloads
+    class C5 {
+      static m(a): void;
+      static m(): void;
+             ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    
+    // merged with namespace, static methods
+    class C6 {
+      static m(): void;
+             ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    namespace C6 {
+    }
+    
+    // merged with namespace, static methods, multiple overloads
+    class C7 {
+      static m(a): void;
+      static m(): void;
+             ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    namespace C7 {
+    }
+    
+    // merged with namespace, static methods, duplicate declarations
+    class C8 {
+      static m(a): void;
+             ~
+!!! error TS2300: Duplicate identifier 'm'.
+      static m(a, b): void;
+             ~
+!!! error TS2300: Duplicate identifier 'm'.
+             ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    namespace C8 {
+      export function m(a?, b?): void { }
+                      ~
+!!! error TS2300: Duplicate identifier 'm'.
+    }
+    
+    // merged with namespace, static methods, duplicate declarations
+    class C9 {
+      static m(a): void { }
+             ~
+!!! error TS2300: Duplicate identifier 'm'.
+    }
+    namespace C9 {
+      export function m(a): void;
+                      ~
+!!! error TS2300: Duplicate identifier 'm'.
+                      ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    
+    // merged namespaces
+    namespace N10 {
+      export function m(a): void;
+                      ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
+    }
+    namespace N10 {
+      export function m(a): void { }
+    }
+    
+    // merged namespaces, duplicate defintions
+    namespace N12 {
+      export function m(a): void;
+                      ~
+!!! error TS2393: Duplicate function implementation.
+      export function m(): void;
+                      ~
+!!! error TS2393: Duplicate function implementation.
+      export function m(a?): void { }
+                      ~
+!!! error TS2393: Duplicate function implementation.
+    }
+    namespace N12 {
+      export function m(a): void { }
+                      ~
+!!! error TS2393: Duplicate function implementation.
+    }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/missingFunctionImplementation.js b/tests/baselines/reference/missingFunctionImplementation.js
new file mode 100644
index 0000000000000..a452c8080b75d
--- /dev/null
+++ b/tests/baselines/reference/missingFunctionImplementation.js
@@ -0,0 +1,168 @@
+//// [missingFunctionImplementation.ts]
+
+export class C1 {
+  m(): void;
+}
+
+// merged with a namespace
+export class C2 {
+  m(): void;
+}
+export namespace C2 { }
+
+
+// merged with a namespace, multiple overloads
+class C3 {
+  m(a, b);
+  m(a);
+}
+namespace C3 { }
+
+// static methods, multiple overloads
+class C4 {
+  static m(a): void;
+}
+
+// static methods, multiple overloads
+class C5 {
+  static m(a): void;
+  static m(): void;
+}
+
+// merged with namespace, static methods
+class C6 {
+  static m(): void;
+}
+namespace C6 {
+}
+
+// merged with namespace, static methods, multiple overloads
+class C7 {
+  static m(a): void;
+  static m(): void;
+}
+namespace C7 {
+}
+
+// merged with namespace, static methods, duplicate declarations
+class C8 {
+  static m(a): void;
+  static m(a, b): void;
+}
+namespace C8 {
+  export function m(a?, b?): void { }
+}
+
+// merged with namespace, static methods, duplicate declarations
+class C9 {
+  static m(a): void { }
+}
+namespace C9 {
+  export function m(a): void;
+}
+
+// merged namespaces
+namespace N10 {
+  export function m(a): void;
+}
+namespace N10 {
+  export function m(a): void { }
+}
+
+// merged namespaces, duplicate defintions
+namespace N12 {
+  export function m(a): void;
+  export function m(): void;
+  export function m(a?): void { }
+}
+namespace N12 {
+  export function m(a): void { }
+}
+
+
+//// [missingFunctionImplementation.js]
+"use strict";
+var C1 = (function () {
+    function C1() {
+    }
+    return C1;
+}());
+exports.C1 = C1;
+// merged with a namespace
+var C2 = (function () {
+    function C2() {
+    }
+    return C2;
+}());
+exports.C2 = C2;
+// merged with a namespace, multiple overloads
+var C3 = (function () {
+    function C3() {
+    }
+    return C3;
+}());
+// static methods, multiple overloads
+var C4 = (function () {
+    function C4() {
+    }
+    return C4;
+}());
+// static methods, multiple overloads
+var C5 = (function () {
+    function C5() {
+    }
+    return C5;
+}());
+// merged with namespace, static methods
+var C6 = (function () {
+    function C6() {
+    }
+    return C6;
+}());
+// merged with namespace, static methods, multiple overloads
+var C7 = (function () {
+    function C7() {
+    }
+    return C7;
+}());
+// merged with namespace, static methods, duplicate declarations
+var C8 = (function () {
+    function C8() {
+    }
+    return C8;
+}());
+var C8;
+(function (C8) {
+    function m(a, b) { }
+    C8.m = m;
+})(C8 || (C8 = {}));
+// merged with namespace, static methods, duplicate declarations
+var C9 = (function () {
+    function C9() {
+    }
+    C9.m = function (a) { };
+    return C9;
+}());
+var C9;
+(function (C9) {
+})(C9 || (C9 = {}));
+// merged namespaces
+var N10;
+(function (N10) {
+})(N10 || (N10 = {}));
+var N10;
+(function (N10) {
+    function m(a) { }
+    N10.m = m;
+})(N10 || (N10 = {}));
+// merged namespaces, duplicate defintions
+var N12;
+(function (N12) {
+    function m(a) { }
+    N12.m = m;
+})(N12 || (N12 = {}));
+var N12;
+(function (N12) {
+    function m(a) { }
+    N12.m = m;
+})(N12 || (N12 = {}));
diff --git a/tests/baselines/reference/missingFunctionImplementation2.errors.txt b/tests/baselines/reference/missingFunctionImplementation2.errors.txt
new file mode 100644
index 0000000000000..a695482e1fba3
--- /dev/null
+++ b/tests/baselines/reference/missingFunctionImplementation2.errors.txt
@@ -0,0 +1,16 @@
+tests/cases/compiler/missingFunctionImplementation2_a.ts(3,19): error TS2384: Overload signatures must all be ambient or non-ambient.
+tests/cases/compiler/missingFunctionImplementation2_b.ts(1,17): error TS2391: Function implementation is missing or not immediately following the declaration.
+
+
+==== tests/cases/compiler/missingFunctionImplementation2_a.ts (1 errors) ====
+    export {};
+    declare module "./missingFunctionImplementation2_b.ts" {
+      export function f(a, b): void;
+                      ~
+!!! error TS2384: Overload signatures must all be ambient or non-ambient.
+    }
+    
+==== tests/cases/compiler/missingFunctionImplementation2_b.ts (1 errors) ====
+    export function f(a?, b?);
+                    ~
+!!! error TS2391: Function implementation is missing or not immediately following the declaration.
\ No newline at end of file
diff --git a/tests/baselines/reference/missingFunctionImplementation2.js b/tests/baselines/reference/missingFunctionImplementation2.js
new file mode 100644
index 0000000000000..104b6dd9443d6
--- /dev/null
+++ b/tests/baselines/reference/missingFunctionImplementation2.js
@@ -0,0 +1,15 @@
+//// [tests/cases/compiler/missingFunctionImplementation2.ts] ////
+
+//// [missingFunctionImplementation2_a.ts]
+export {};
+declare module "./missingFunctionImplementation2_b.ts" {
+  export function f(a, b): void;
+}
+
+//// [missingFunctionImplementation2_b.ts]
+export function f(a?, b?);
+
+//// [missingFunctionImplementation2_a.js]
+"use strict";
+//// [missingFunctionImplementation2_b.js]
+"use strict";
diff --git a/tests/cases/compiler/missingFunctionImplementation.ts b/tests/cases/compiler/missingFunctionImplementation.ts
new file mode 100644
index 0000000000000..e261db3a6670e
--- /dev/null
+++ b/tests/cases/compiler/missingFunctionImplementation.ts
@@ -0,0 +1,79 @@
+
+export class C1 {
+  m(): void;
+}
+
+// merged with a namespace
+export class C2 {
+  m(): void;
+}
+export namespace C2 { }
+
+
+// merged with a namespace, multiple overloads
+class C3 {
+  m(a, b);
+  m(a);
+}
+namespace C3 { }
+
+// static methods, multiple overloads
+class C4 {
+  static m(a): void;
+}
+
+// static methods, multiple overloads
+class C5 {
+  static m(a): void;
+  static m(): void;
+}
+
+// merged with namespace, static methods
+class C6 {
+  static m(): void;
+}
+namespace C6 {
+}
+
+// merged with namespace, static methods, multiple overloads
+class C7 {
+  static m(a): void;
+  static m(): void;
+}
+namespace C7 {
+}
+
+// merged with namespace, static methods, duplicate declarations
+class C8 {
+  static m(a): void;
+  static m(a, b): void;
+}
+namespace C8 {
+  export function m(a?, b?): void { }
+}
+
+// merged with namespace, static methods, duplicate declarations
+class C9 {
+  static m(a): void { }
+}
+namespace C9 {
+  export function m(a): void;
+}
+
+// merged namespaces
+namespace N10 {
+  export function m(a): void;
+}
+namespace N10 {
+  export function m(a): void { }
+}
+
+// merged namespaces, duplicate defintions
+namespace N12 {
+  export function m(a): void;
+  export function m(): void;
+  export function m(a?): void { }
+}
+namespace N12 {
+  export function m(a): void { }
+}
diff --git a/tests/cases/compiler/missingFunctionImplementation2.ts b/tests/cases/compiler/missingFunctionImplementation2.ts
new file mode 100644
index 0000000000000..25909b6add4c2
--- /dev/null
+++ b/tests/cases/compiler/missingFunctionImplementation2.ts
@@ -0,0 +1,8 @@
+// @Filename: missingFunctionImplementation2_a.ts
+export {};
+declare module "./missingFunctionImplementation2_b.ts" {
+  export function f(a, b): void;
+}
+
+// @Filename: missingFunctionImplementation2_b.ts
+export function f(a?, b?);
\ No newline at end of file