diff --git a/packages/uniquify/src/uniquify.ts b/packages/uniquify/src/uniquify.ts
index 5727f229..8e754f56 100644
--- a/packages/uniquify/src/uniquify.ts
+++ b/packages/uniquify/src/uniquify.ts
@@ -171,7 +171,7 @@ const uniquify = ({
             const existingValueMatch = value.match(valueIdxRegex);
             if (existingValueMatch) {
                 const existingValueIdx = parseInt(
-                    existingValueMatch[0].substr(separator.length),
+                    existingValueMatch[0].substring(separator.length),
                     10,
                 );