diff --git a/src/rules/extensions.ts b/src/rules/extensions.ts
index 73bb6a75..f0c6fa35 100644
--- a/src/rules/extensions.ts
+++ b/src/rules/extensions.ts
@@ -328,9 +328,9 @@ export default createRule<Options, MessageId>({
 
         const resolvedPath = resolve(importPath, context)
 
-        // get extension from resolved path, if possible.
-        // for unresolved, use source value.
-        const extension = path.extname(resolvedPath || importPath).slice(1)
+        const extension =
+          path.extname(importPath).slice(1) ||
+          (resolvedPath ? path.extname(resolvedPath).slice(1) : '')
 
         // determine if this is a module
         const isPackage =