diff --git a/packages/quicktype-core/src/language/JavaScript.ts b/packages/quicktype-core/src/language/JavaScript.ts
index 12a18e320..304a6c775 100644
--- a/packages/quicktype-core/src/language/JavaScript.ts
+++ b/packages/quicktype-core/src/language/JavaScript.ts
@@ -65,9 +65,17 @@ export type JavaScriptTypeAnnotations = {
     never: string;
 };
 
-export class JavaScriptTargetLanguage extends TargetLanguage<"JavaScript", ["javascript", "js", "jsx"], "js"> {
-    constructor() {
-        super("JavaScript", ["javascript", "js", "jsx"], "js");
+export class JavaScriptTargetLanguage<
+    DisplayName extends string = "JavaScript",
+    Names extends readonly string[] = readonly ["javascript", "js", "jsx"],
+    Extension extends string = "js"
+> extends TargetLanguage<DisplayName, Names, Extension> {
+    constructor(
+        displayName = "JavaScript" as DisplayName,
+        names = ["javascript", "js", "jsx"] as unknown as Names,
+        extension = "js" as Extension
+    ) {
+        super(displayName, names, extension);
     }
 
     protected getOptions(): Option<any>[] {
diff --git a/packages/quicktype-core/src/language/TypeScriptFlow.ts b/packages/quicktype-core/src/language/TypeScriptFlow.ts
index f21202056..664ff92d2 100644
--- a/packages/quicktype-core/src/language/TypeScriptFlow.ts
+++ b/packages/quicktype-core/src/language/TypeScriptFlow.ts
@@ -40,7 +40,15 @@ const tsFlowTypeAnnotations = {
     boolean: ": boolean"
 };
 
-export abstract class TypeScriptFlowBaseTargetLanguage extends JavaScriptTargetLanguage {
+export abstract class TypeScriptFlowBaseTargetLanguage<
+    DisplayName extends string,
+    Names extends readonly string[],
+    Extension extends string
+> extends JavaScriptTargetLanguage<DisplayName, Names, Extension> {
+    protected constructor(displayName: DisplayName, names: Names, extension: Extension) {
+        super(displayName, names, extension);
+    }
+
     protected getOptions(): Option<any>[] {
         return [
             tsFlowOptions.justTypes,
@@ -68,7 +76,11 @@ export abstract class TypeScriptFlowBaseTargetLanguage extends JavaScriptTargetL
     ): JavaScriptRenderer;
 }
 
-export class TypeScriptTargetLanguage extends TypeScriptFlowBaseTargetLanguage {
+export class TypeScriptTargetLanguage extends TypeScriptFlowBaseTargetLanguage<
+    "TypeScript",
+    ["typescript", "ts", "tsx"],
+    "ts"
+> {
     constructor() {
         super("TypeScript", ["typescript", "ts", "tsx"], "ts");
     }
@@ -339,7 +351,7 @@ export class TypeScriptRenderer extends TypeScriptFlowBaseRenderer {
     }
 }
 
-export class FlowTargetLanguage extends TypeScriptFlowBaseTargetLanguage {
+export class FlowTargetLanguage extends TypeScriptFlowBaseTargetLanguage<"Flow", ["flow"], "js"> {
     constructor() {
         super("Flow", ["flow"], "js");
     }