diff --git a/index.js b/index.js
index 25006c7c..ae0ea28c 100644
--- a/index.js
+++ b/index.js
@@ -47,11 +47,16 @@ function applyUserConfig(config, userConfig, servicePath, runtime) {
   const runtimeVersion =
     Number.parseInt((runtime || "").replace("nodejs", ""), 10) || 12;
 
+  // Exclude aws-sdk from default if runtime >= 18
+  const forceExclude = config.options.forceExclude.filter(
+    (item) => !(runtimeVersion >= 18 && item === "aws-sdk")
+  );
+
   // Concat forceExclude if provided
   if (userConfig.forceExclude) {
-    userConfig.forceExclude = config.options.forceExclude
-      .filter((item) => !(runtimeVersion >= 18 && item === "aws-sdk"))
-      .concat(userConfig.forceExclude);
+    userConfig.forceExclude = forceExclude.concat(userConfig.forceExclude);
+  } else {
+    userConfig.forceExclude = forceExclude;
   }
 
   // Concat externals if a list of packages are provided