diff --git a/src/compiler/checker.ts b/src/compiler/checker.ts
index 18c3b6e1ec685..35d54c3468774 100644
--- a/src/compiler/checker.ts
+++ b/src/compiler/checker.ts
@@ -1763,6 +1763,7 @@ export function createTypeChecker(host: TypeCheckerHost): TypeChecker {
         getImmediateAliasedSymbol,
         getAliasedSymbol: resolveAlias,
         getEmitResolver,
+        requiresAddingImplicitUndefined,
         getExportsOfModule: getExportsOfModuleAsArray,
         getExportsAndPropertiesOfModule,
         forEachExportAndPropertyOfModule,
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 4994322657070..9df1b4a8e7f31 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -5265,6 +5265,7 @@ export interface TypeChecker {
     /** @internal */ getDiagnostics(sourceFile?: SourceFile, cancellationToken?: CancellationToken): Diagnostic[];
     /** @internal */ getGlobalDiagnostics(): Diagnostic[];
     /** @internal */ getEmitResolver(sourceFile?: SourceFile, cancellationToken?: CancellationToken, forceDts?: boolean): EmitResolver;
+    /** @internal */ requiresAddingImplicitUndefined(parameter: ParameterDeclaration | JSDocParameterTag): boolean;
 
     /** @internal */ getNodeCount(): number;
     /** @internal */ getIdentifierCount(): number;
diff --git a/src/services/codefixes/fixMissingTypeAnnotationOnExports.ts b/src/services/codefixes/fixMissingTypeAnnotationOnExports.ts
index 1b2f93d06c78d..70ceb0c31eba3 100644
--- a/src/services/codefixes/fixMissingTypeAnnotationOnExports.ts
+++ b/src/services/codefixes/fixMissingTypeAnnotationOnExports.ts
@@ -183,7 +183,7 @@ registerCodeFix({
 
         addCodeAction(addInlineTypeAssertion, fixes, context, TypePrintMode.Full, f => f.addInlineAssertion(context.span));
         addCodeAction(addInlineTypeAssertion, fixes, context, TypePrintMode.Relative, f => f.addInlineAssertion(context.span));
-        addCodeAction(addAnnotationFix, fixes, context, TypePrintMode.Widened, f => f.addInlineAssertion(context.span));
+        addCodeAction(addInlineTypeAssertion, fixes, context, TypePrintMode.Widened, f => f.addInlineAssertion(context.span));
 
         addCodeAction(extractExpression, fixes, context, TypePrintMode.Full, f => f.extractAsVariable(context.span));
 
@@ -237,7 +237,6 @@ function withContext<T>(
     const sourceFile: SourceFile = context.sourceFile;
     const program = context.program;
     const typeChecker: TypeChecker = program.getTypeChecker();
-    const emitResolver = typeChecker.getEmitResolver();
     const scriptTarget = getEmitScriptTarget(program.getCompilerOptions());
     const importAdder = createImportAdder(context.sourceFile, context.program, context.preferences, context.host);
     const fixedNodes = new Set<Node>();
@@ -887,7 +886,7 @@ function withContext<T>(
             type = widenedType;
         }
 
-        if (isParameter(node) && emitResolver.requiresAddingImplicitUndefined(node)) {
+        if (isParameter(node) && typeChecker.requiresAddingImplicitUndefined(node)) {
             type = typeChecker.getUnionType([typeChecker.getUndefinedType(), type], UnionReduction.None);
         }
         const flags = (
@@ -1108,26 +1107,26 @@ function withContext<T>(
         setEmitFlags(node, EmitFlags.None);
         return result;
     }
-}
 
-// Some --isolatedDeclarations errors are not present on the node that directly needs type annotation, so look in the
-// ancestors to look for node that needs type annotation. This function can return undefined if the AST is ill-formed.
-function findAncestorWithMissingType(node: Node): Node | undefined {
-    return findAncestor(node, n => {
-        return canHaveTypeAnnotation.has(n.kind) &&
-            ((!isObjectBindingPattern(n) && !isArrayBindingPattern(n)) || isVariableDeclaration(n.parent));
-    });
-}
-
-function findBestFittingNode(node: Node, span: TextSpan) {
-    while (node && node.end < span.start + span.length) {
-        node = node.parent;
-    }
-    while (node.parent.pos === node.pos && node.parent.end === node.end) {
-        node = node.parent;
+    // Some --isolatedDeclarations errors are not present on the node that directly needs type annotation, so look in the
+    // ancestors to look for node that needs type annotation. This function can return undefined if the AST is ill-formed.
+    function findAncestorWithMissingType(node: Node): Node | undefined {
+        return findAncestor(node, n => {
+            return canHaveTypeAnnotation.has(n.kind) &&
+                ((!isObjectBindingPattern(n) && !isArrayBindingPattern(n)) || isVariableDeclaration(n.parent));
+        });
     }
-    if (isIdentifier(node) && hasInitializer(node.parent) && node.parent.initializer) {
-        return node.parent.initializer;
+
+    function findBestFittingNode(node: Node, span: TextSpan) {
+        while (node && node.end < span.start + span.length) {
+            node = node.parent;
+        }
+        while (node.parent.pos === node.pos && node.parent.end === node.end) {
+            node = node.parent;
+        }
+        if (isIdentifier(node) && hasInitializer(node.parent) && node.parent.initializer) {
+            return node.parent.initializer;
+        }
+        return node;
     }
-    return node;
 }