diff --git a/packages/eslint-plugin/src/rules/unified-signatures.ts b/packages/eslint-plugin/src/rules/unified-signatures.ts
index 8d8cda0e378..3b5f2294762 100644
--- a/packages/eslint-plugin/src/rules/unified-signatures.ts
+++ b/packages/eslint-plugin/src/rules/unified-signatures.ts
@@ -213,9 +213,9 @@ export default util.createRule<Options, MessageIds>({
         b.typeParameters !== undefined ? b.typeParameters.params : undefined;
 
       if (ignoreDifferentlyNamedParameters) {
-        for (let i = 0; i < a.params.length; i += 1) {
+        const commonParamsLength = Math.min(a.params.length, b.params.length);
+        for (let i = 0; i < commonParamsLength; i += 1) {
           if (
-            b.params[i] &&
             a.params[i].type === b.params[i].type &&
             getStaticParameterName(a.params[i]) !==
               getStaticParameterName(b.params[i])