diff --git a/packages/openapi-ts-tests/main/test/2.0.x.test.ts b/packages/openapi-ts-tests/main/test/2.0.x.test.ts
index 9edb12831..916d1645a 100644
--- a/packages/openapi-ts-tests/main/test/2.0.x.test.ts
+++ b/packages/openapi-ts-tests/main/test/2.0.x.test.ts
@@ -300,7 +300,7 @@ describe(`OpenAPI ${version}`, () => {
               );
               // Deduplicate prefixes: Foo_Foo → Foo
               const m = clean.match(/^([A-Za-z\d]+)_\1([A-Za-z\d]*)$/);
-              if (m) clean = m[1] + m[2];
+              if (m?.[1] && m?.[2] !== undefined) clean = m[1] + m[2];
               return clean;
             },
           },
diff --git a/packages/openapi-ts-tests/main/test/3.0.x.test.ts b/packages/openapi-ts-tests/main/test/3.0.x.test.ts
index 22fff3851..b39fcff4e 100644
--- a/packages/openapi-ts-tests/main/test/3.0.x.test.ts
+++ b/packages/openapi-ts-tests/main/test/3.0.x.test.ts
@@ -603,7 +603,7 @@ describe(`OpenAPI ${version}`, () => {
               );
               // Deduplicate prefixes: Foo_Foo → Foo
               const m = clean.match(/^([A-Za-z\d]+)_\1([A-Za-z\d]*)$/);
-              if (m) clean = m[1] + m[2];
+              if (m?.[1] && m?.[2] !== undefined) clean = m[1] + m[2];
               return clean;
             },
           },
diff --git a/packages/openapi-ts-tests/main/test/3.1.x.test.ts b/packages/openapi-ts-tests/main/test/3.1.x.test.ts
index 0ed636eae..2a42d0494 100644
--- a/packages/openapi-ts-tests/main/test/3.1.x.test.ts
+++ b/packages/openapi-ts-tests/main/test/3.1.x.test.ts
@@ -705,7 +705,7 @@ describe(`OpenAPI ${version}`, () => {
               );
               // Deduplicate prefixes: Foo_Foo → Foo
               const m = clean.match(/^([A-Za-z\d]+)_\1([A-Za-z\d]*)$/);
-              if (m) clean = m[1] + m[2];
+              if (m?.[1] && m?.[2] !== undefined) clean = m[1] + m[2];
               return clean;
             },
           },