diff --git a/src/compiler/program.ts b/src/compiler/program.ts
index c77fa8371185e..a495c61c07d4f 100644
--- a/src/compiler/program.ts
+++ b/src/compiler/program.ts
@@ -958,7 +958,6 @@ namespace ts {
             getResolvedTypeReferenceDirectives: () => resolvedTypeReferenceDirectives,
             isSourceFileFromExternalLibrary,
             isSourceFileDefaultLibrary,
-            dropDiagnosticsProducingTypeChecker,
             getSourceFileFromReference,
             getLibFileFromReference,
             sourceFileToPackageName,
@@ -1558,12 +1557,8 @@ namespace ts {
             return diagnosticsProducingTypeChecker || (diagnosticsProducingTypeChecker = createTypeChecker(program, /*produceDiagnostics:*/ true));
         }
 
-        function dropDiagnosticsProducingTypeChecker() {
-            diagnosticsProducingTypeChecker = undefined!;
-        }
-
         function getTypeChecker() {
-            return noDiagnosticsTypeChecker || (noDiagnosticsTypeChecker = createTypeChecker(program, /*produceDiagnostics:*/ false));
+            return noDiagnosticsTypeChecker || (noDiagnosticsTypeChecker = diagnosticsProducingTypeChecker || createTypeChecker(program, /*produceDiagnostics:*/ false));
         }
 
         function emit(sourceFile?: SourceFile, writeFileCallback?: WriteFileCallback, cancellationToken?: CancellationToken, emitOnlyDtsFiles?: boolean, transformers?: CustomTransformers, forceDtsEmit?: boolean): EmitResult {
diff --git a/src/compiler/types.ts b/src/compiler/types.ts
index 32a36306a17d5..166cc0c4c25f0 100644
--- a/src/compiler/types.ts
+++ b/src/compiler/types.ts
@@ -3222,7 +3222,6 @@ namespace ts {
         // For testing purposes only.  Should not be used by any other consumers (including the
         // language service).
         /* @internal */ getDiagnosticsProducingTypeChecker(): TypeChecker;
-        /* @internal */ dropDiagnosticsProducingTypeChecker(): void;
 
         /* @internal */ getClassifiableNames(): UnderscoreEscapedMap<true>;
 
diff --git a/src/harness/harnessIO.ts b/src/harness/harnessIO.ts
index 29cdd9cf614d5..b95a4fdea238a 100644
--- a/src/harness/harnessIO.ts
+++ b/src/harness/harnessIO.ts
@@ -710,7 +710,7 @@ namespace Harness {
             // These types are equivalent, but depend on what order the compiler observed
             // certain parts of the program.
 
-            const fullWalker = new TypeWriterWalker(program, /*fullTypeCheck*/ true, !!hasErrorBaseline);
+            const fullWalker = new TypeWriterWalker(program, !!hasErrorBaseline);
 
             // Produce baselines.  The first gives the types for all expressions.
             // The second gives symbols for all identifiers.
diff --git a/src/harness/typeWriter.ts b/src/harness/typeWriter.ts
index b45f87a19f275..02d3d599ef9a3 100644
--- a/src/harness/typeWriter.ts
+++ b/src/harness/typeWriter.ts
@@ -39,12 +39,10 @@ namespace Harness {
 
         private checker: ts.TypeChecker;
 
-        constructor(private program: ts.Program, fullTypeCheck: boolean, private hadErrorBaseline: boolean) {
+        constructor(private program: ts.Program, private hadErrorBaseline: boolean) {
             // Consider getting both the diagnostics checker and the non-diagnostics checker to verify
             // they are consistent.
-            this.checker = fullTypeCheck
-                ? program.getDiagnosticsProducingTypeChecker()
-                : program.getTypeChecker();
+            this.checker = program.getDiagnosticsProducingTypeChecker();
         }
 
         public *getSymbols(fileName: string): IterableIterator<TypeWriterSymbolResult> {