diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index fe5c9e1e43..da3dac4d60 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -6420,11 +6420,11 @@ namespace ts {
          * @param typeParameters The requested type parameters.
          * @param minTypeArgumentCount The minimum number of required type arguments.
          */
-        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScript: boolean) {
+        function fillMissingTypeArguments(typeArguments: Type[] | undefined, typeParameters: TypeParameter[] | undefined, minTypeArgumentCount: number, isJavaScriptImplicitAny: boolean) {
             const numTypeParameters = length(typeParameters);
             if (numTypeParameters) {
                 const numTypeArguments = length(typeArguments);
-                if ((isJavaScript || numTypeArguments >= minTypeArgumentCount) && numTypeArguments <= numTypeParameters) {
+                if ((isJavaScriptImplicitAny || numTypeArguments >= minTypeArgumentCount) && numTypeArguments <= numTypeParameters) {
                     if (!typeArguments) {
                         typeArguments = [];
                     }
@@ -6433,12 +6433,12 @@ namespace ts {
                     // If a type parameter does not have a default type, or if the default type
                     // is a forward reference, the empty object type is used.
                     for (let i = numTypeArguments; i < numTypeParameters; i++) {
-                        typeArguments[i] = getDefaultTypeArgumentType(isJavaScript);
+                        typeArguments[i] = getDefaultTypeArgumentType(isJavaScriptImplicitAny);
                     }
                     for (let i = numTypeArguments; i < numTypeParameters; i++) {
                         const mapper = createTypeMapper(typeParameters, typeArguments);
                         const defaultType = getDefaultFromTypeParameter(typeParameters[i]);
-                        typeArguments[i] = defaultType ? instantiateType(defaultType, mapper) : getDefaultTypeArgumentType(isJavaScript);
+                        typeArguments[i] = defaultType ? instantiateType(defaultType, mapper) : getDefaultTypeArgumentType(isJavaScriptImplicitAny);
                     }
                 }
             }
@@ -6874,21 +6874,25 @@ namespace ts {
             if (typeParameters) {
                 const numTypeArguments = length(node.typeArguments);
                 const minTypeArgumentCount = getMinTypeArgumentCount(typeParameters);
-                const isJavascript = isInJavaScriptFile(node);
-                if (!isJavascript && (numTypeArguments < minTypeArgumentCount || numTypeArguments > typeParameters.length)) {
-                    error(node,
-                        minTypeArgumentCount === typeParameters.length
-                            ? Diagnostics.Generic_type_0_requires_1_type_argument_s
-                            : Diagnostics.Generic_type_0_requires_between_1_and_2_type_arguments,
-                        typeToString(type, /*enclosingDeclaration*/ undefined, TypeFormatFlags.WriteArrayAsGenericType),
-                        minTypeArgumentCount,
-                        typeParameters.length);
+                const isJs = isInJavaScriptFile(node);
+                const isJsImplicitAny = !compilerOptions.noImplicitAny && isJs;
+                if (!isJsImplicitAny && (numTypeArguments < minTypeArgumentCount || numTypeArguments > typeParameters.length)) {
+                    const missingAugmentsTag = isJs && node.parent.kind !== SyntaxKind.JSDocAugmentsTag;
+                    const diag = minTypeArgumentCount === typeParameters.length
+                        ? missingAugmentsTag
+                            ? Diagnostics.Expected_0_type_arguments_provide_these_with_an_extends_tag
+                            : Diagnostics.Generic_type_0_requires_1_type_argument_s
+                        : missingAugmentsTag
+                            ? Diagnostics.Expected_0_1_type_arguments_provide_these_with_an_extends_tag
+                            : Diagnostics.Generic_type_0_requires_between_1_and_2_type_arguments;
+                    const typeStr = typeToString(type, /*enclosingDeclaration*/ undefined, TypeFormatFlags.WriteArrayAsGenericType);
+                    error(node, diag, typeStr, minTypeArgumentCount, typeParameters.length);
                     return unknownType;
                 }
                 // In a type reference, the outer type parameters of the referenced class or interface are automatically
                 // supplied as type arguments and the type reference only specifies arguments for the local type parameters
                 // of the class or interface.
-                const typeArguments = concatenate(type.outerTypeParameters, fillMissingTypeArguments(typeArgs, typeParameters, minTypeArgumentCount, isJavascript));
+                const typeArguments = concatenate(type.outerTypeParameters, fillMissingTypeArguments(typeArgs, typeParameters, minTypeArgumentCount, isJsImplicitAny));
                 return createTypeReference(<GenericType>type, typeArguments);
             }
             if (node.typeArguments) {
diff --git a/src/compiler/diagnosticMessages.json b/src/compiler/diagnosticMessages.json
index 3b6ecffcfb..0f88d5e4ac 100644
--- a/src/compiler/diagnosticMessages.json
+++ b/src/compiler/diagnosticMessages.json
@@ -3539,6 +3539,14 @@
         "category": "Error",
         "code": 8025
     },
+    "Expected {0} type arguments; provide these with an '@extends' tag.": {
+        "category": "Error",
+        "code": 8026
+    },
+    "Expected {0}-{1} type arguments; provide these with an '@extends' tag.": {
+        "category": "Error",
+        "code": 8027
+    },
     "Only identifiers/qualified-names with optional type arguments are currently supported in a class 'extends' clause.": {
         "category": "Error",
         "code": 9002
diff --git a/tests/baselines/reference/jsExtendsImplicitAny.errors.txt b/tests/baselines/reference/jsExtendsImplicitAny.errors.txt
new file mode 100644
index 0000000000..4b836970e0
--- /dev/null
+++ b/tests/baselines/reference/jsExtendsImplicitAny.errors.txt
@@ -0,0 +1,17 @@
+/b.js(1,17): error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
+/b.js(3,15): error TS2314: Generic type 'A<T>' requires 1 type argument(s).
+
+
+==== /a.d.ts (0 errors) ====
+    declare class A<T> { x: T; }
+    
+==== /b.js (2 errors) ====
+    class B extends A {}
+                    ~
+!!! error TS8026: Expected A<T> type arguments; provide these with an '@extends' tag.
+    
+    /** @augments A */
+                  ~
+!!! error TS2314: Generic type 'A<T>' requires 1 type argument(s).
+    class C { }
+    
\ No newline at end of file
diff --git a/tests/baselines/reference/jsExtendsImplicitAny.symbols b/tests/baselines/reference/jsExtendsImplicitAny.symbols
new file mode 100644
index 0000000000..0a6d71e109
--- /dev/null
+++ b/tests/baselines/reference/jsExtendsImplicitAny.symbols
@@ -0,0 +1,16 @@
+=== /a.d.ts ===
+declare class A<T> { x: T; }
+>A : Symbol(A, Decl(a.d.ts, 0, 0))
+>T : Symbol(T, Decl(a.d.ts, 0, 16))
+>x : Symbol(A.x, Decl(a.d.ts, 0, 20))
+>T : Symbol(T, Decl(a.d.ts, 0, 16))
+
+=== /b.js ===
+class B extends A {}
+>B : Symbol(B, Decl(b.js, 0, 0))
+>A : Symbol(A, Decl(a.d.ts, 0, 0))
+
+/** @augments A */
+class C { }
+>C : Symbol(C, Decl(b.js, 0, 20))
+
diff --git a/tests/baselines/reference/jsExtendsImplicitAny.types b/tests/baselines/reference/jsExtendsImplicitAny.types
new file mode 100644
index 0000000000..ba98ef3ed2
--- /dev/null
+++ b/tests/baselines/reference/jsExtendsImplicitAny.types
@@ -0,0 +1,16 @@
+=== /a.d.ts ===
+declare class A<T> { x: T; }
+>A : A<T>
+>T : T
+>x : T
+>T : T
+
+=== /b.js ===
+class B extends A {}
+>B : B
+>A : typeof A
+
+/** @augments A */
+class C { }
+>C : C
+
diff --git a/tests/cases/compiler/jsExtendsImplicitAny.ts b/tests/cases/compiler/jsExtendsImplicitAny.ts
new file mode 100644
index 0000000000..e3d737ceb3
--- /dev/null
+++ b/tests/cases/compiler/jsExtendsImplicitAny.ts
@@ -0,0 +1,13 @@
+// @allowJs: true
+// @checkJs: true
+// @noEmit: true
+// @noImplicitAny: true
+
+// @Filename: /a.d.ts
+declare class A<T> { x: T; }
+
+// @Filename: /b.js
+class B extends A {}
+
+/** @augments A */
+class C { }