diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index 3c3c1ff5db..fa86ef147c 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -599,7 +599,7 @@ namespace ts {
         const cachedSemanticDiagnosticsForFile: DiagnosticCache<Diagnostic> = {};
         const cachedDeclarationDiagnosticsForFile: DiagnosticCache<DiagnosticWithLocation> = {};
 
-        let resolvedTypeReferenceDirectives = createMap<ResolvedTypeReferenceDirective>();
+        let resolvedTypeReferenceDirectives = createMap<ResolvedTypeReferenceDirective | undefined>();
         let fileProcessingDiagnostics = createDiagnosticCollection();
 
         // The below settings are to track if a .js file should be add to the program if loaded via searching under node_modules.
@@ -656,7 +656,7 @@ namespace ts {
             resolveModuleNamesWorker = (moduleNames, containingFile, _reusedNames, redirectedReference) => loadWithLocalCache<ResolvedModuleFull>(Debug.assertEachDefined(moduleNames), containingFile, redirectedReference, loader);
         }
 
-        let resolveTypeReferenceDirectiveNamesWorker: (typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference) => ResolvedTypeReferenceDirective[];
+        let resolveTypeReferenceDirectiveNamesWorker: (typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference) => (ResolvedTypeReferenceDirective | undefined)[];
         if (host.resolveTypeReferenceDirectives) {
             resolveTypeReferenceDirectiveNamesWorker = (typeDirectiveNames, containingFile, redirectedReference) => host.resolveTypeReferenceDirectives!(Debug.assertEachDefined(typeDirectiveNames), containingFile, redirectedReference);
         }
@@ -2335,7 +2335,7 @@ namespace ts {
             }
         }
 
-        function processTypeReferenceDirective(typeReferenceDirective: string, resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective,
+        function processTypeReferenceDirective(typeReferenceDirective: string, resolvedTypeReferenceDirective?: ResolvedTypeReferenceDirective,
             refFile?: SourceFile, refPos?: number, refEnd?: number): void {
 
             // If we already found this library as a primary reference - nothing to do
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 1c2009bc19..e025ba8a4c 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -2714,7 +2714,7 @@ namespace ts {
         // It is used to resolve module names in the checker.
         // Content of this field should never be used directly - use getResolvedModuleFileName/setResolvedModuleFileName functions instead
         /* @internal */ resolvedModules?: Map<ResolvedModuleFull | undefined>;
-        /* @internal */ resolvedTypeReferenceDirectiveNames: Map<ResolvedTypeReferenceDirective>;
+        /* @internal */ resolvedTypeReferenceDirectiveNames: Map<ResolvedTypeReferenceDirective | undefined>;
         /* @internal */ imports: ReadonlyArray<StringLiteralLike>;
         /**
          * When a file's references are redirected due to project reference directives,
@@ -2889,7 +2889,7 @@ namespace ts {
         /* @internal */ getTypeCount(): number;
 
         /* @internal */ getFileProcessingDiagnostics(): DiagnosticCollection;
-        /* @internal */ getResolvedTypeReferenceDirectives(): Map<ResolvedTypeReferenceDirective>;
+        /* @internal */ getResolvedTypeReferenceDirectives(): Map<ResolvedTypeReferenceDirective | undefined>;
         isSourceFileFromExternalLibrary(file: SourceFile): boolean;
         isSourceFileDefaultLibrary(file: SourceFile): boolean;
 
@@ -2997,7 +2997,7 @@ namespace ts {
 
         getSourceFiles(): ReadonlyArray<SourceFile>;
         getSourceFile(fileName: string): SourceFile | undefined;
-        getResolvedTypeReferenceDirectives(): ReadonlyMap<ResolvedTypeReferenceDirective>;
+        getResolvedTypeReferenceDirectives(): ReadonlyMap<ResolvedTypeReferenceDirective | undefined>;
 
         readonly redirectTargetsMap: RedirectTargetsMap;
     }
@@ -4979,7 +4979,7 @@ namespace ts {
         /**
          * This method is a companion for 'resolveModuleNames' and is used to resolve 'types' references to actual type declaration files
          */
-        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): ResolvedTypeReferenceDirective[];
+        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): (ResolvedTypeReferenceDirective | undefined)[];
         getEnvironmentVariable?(name: string): string | undefined;
         /* @internal */ onReleaseOldSourceFile?(oldSourceFile: SourceFile, oldOptions: CompilerOptions, hasSourceFileByPath: boolean): void;
         /* @internal */ hasInvalidatedResolution?: HasInvalidatedResolution;
diff --git a/src/compiler/utilities.ts b/src/compiler/utilities.ts
index 6310d299b4..bd1d874e9d 100644
--- a/src/compiler/utilities.ts
+++ b/src/compiler/utilities.ts
@@ -227,9 +227,9 @@ namespace ts {
         sourceFile.resolvedModules.set(moduleNameText, resolvedModule);
     }
 
-    export function setResolvedTypeReferenceDirective(sourceFile: SourceFile, typeReferenceDirectiveName: string, resolvedTypeReferenceDirective: ResolvedTypeReferenceDirective): void {
+    export function setResolvedTypeReferenceDirective(sourceFile: SourceFile, typeReferenceDirectiveName: string, resolvedTypeReferenceDirective?: ResolvedTypeReferenceDirective): void {
         if (!sourceFile.resolvedTypeReferenceDirectiveNames) {
-            sourceFile.resolvedTypeReferenceDirectiveNames = createMap<ResolvedTypeReferenceDirective>();
+            sourceFile.resolvedTypeReferenceDirectiveNames = createMap<ResolvedTypeReferenceDirective | undefined>();
         }
 
         sourceFile.resolvedTypeReferenceDirectiveNames.set(typeReferenceDirectiveName, resolvedTypeReferenceDirective);
diff --git a/tests/baselines/reference/api/tsserverlibrary.d.ts b/tests/baselines/reference/api/tsserverlibrary.d.ts
index 1680826b31..bd9067a20c 100644
--- a/tests/baselines/reference/api/tsserverlibrary.d.ts
+++ b/tests/baselines/reference/api/tsserverlibrary.d.ts
@@ -2694,7 +2694,7 @@ declare namespace ts {
         /**
          * This method is a companion for 'resolveModuleNames' and is used to resolve 'types' references to actual type declaration files
          */
-        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): ResolvedTypeReferenceDirective[];
+        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): (ResolvedTypeReferenceDirective | undefined)[];
         getEnvironmentVariable?(name: string): string | undefined;
         createHash?(data: string): string;
     }
@@ -4656,9 +4656,9 @@ declare namespace ts {
         realpath?(path: string): string;
         fileExists?(path: string): boolean;
         getTypeRootsVersion?(): number;
-        resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames?: string[], redirectedReference?: ResolvedProjectReference): ResolvedModule[];
+        resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames?: string[], redirectedReference?: ResolvedProjectReference): (ResolvedModule | undefined)[];
         getResolvedModuleWithFailedLookupLocationsFromCache?(modulename: string, containingFile: string): ResolvedModuleWithFailedLookupLocations | undefined;
-        resolveTypeReferenceDirectives?(typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): ResolvedTypeReferenceDirective[];
+        resolveTypeReferenceDirectives?(typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): (ResolvedTypeReferenceDirective | undefined)[];
         getDirectories?(directoryName: string): string[];
         /**
          * Gets a set of custom transformers to use during emit.
diff --git a/tests/baselines/reference/api/typescript.d.ts b/tests/baselines/reference/api/typescript.d.ts
index a7c3f9cd90..0d24af21ee 100644
--- a/tests/baselines/reference/api/typescript.d.ts
+++ b/tests/baselines/reference/api/typescript.d.ts
@@ -2694,7 +2694,7 @@ declare namespace ts {
         /**
          * This method is a companion for 'resolveModuleNames' and is used to resolve 'types' references to actual type declaration files
          */
-        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): ResolvedTypeReferenceDirective[];
+        resolveTypeReferenceDirectives?(typeReferenceDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): (ResolvedTypeReferenceDirective | undefined)[];
         getEnvironmentVariable?(name: string): string | undefined;
         createHash?(data: string): string;
     }
@@ -4656,9 +4656,9 @@ declare namespace ts {
         realpath?(path: string): string;
         fileExists?(path: string): boolean;
         getTypeRootsVersion?(): number;
-        resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames?: string[], redirectedReference?: ResolvedProjectReference): ResolvedModule[];
+        resolveModuleNames?(moduleNames: string[], containingFile: string, reusedNames?: string[], redirectedReference?: ResolvedProjectReference): (ResolvedModule | undefined)[];
         getResolvedModuleWithFailedLookupLocationsFromCache?(modulename: string, containingFile: string): ResolvedModuleWithFailedLookupLocations | undefined;
-        resolveTypeReferenceDirectives?(typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): ResolvedTypeReferenceDirective[];
+        resolveTypeReferenceDirectives?(typeDirectiveNames: string[], containingFile: string, redirectedReference?: ResolvedProjectReference): (ResolvedTypeReferenceDirective | undefined)[];
         getDirectories?(directoryName: string): string[];
         /**
          * Gets a set of custom transformers to use during emit.