diff --git a/README.md b/README.md
index 8c5d24d..207801d 100644
--- a/README.md
+++ b/README.md
@@ -57,7 +57,7 @@ module.exports = {
       skipFiles: [],
       c: false,
       json: false,
-      optimization: "O2",
+      optimization: "O1",
     },
     setupSettings: {
       contributionSettings: {
diff --git a/package-lock.json b/package-lock.json
index b3ad23a..e061402 100644
--- a/package-lock.json
+++ b/package-lock.json
@@ -1,12 +1,12 @@
 {
   "name": "@solarity/hardhat-zkit",
-  "version": "0.4.11",
+  "version": "0.4.12",
   "lockfileVersion": 3,
   "requires": true,
   "packages": {
     "": {
       "name": "@solarity/hardhat-zkit",
-      "version": "0.4.11",
+      "version": "0.4.12",
       "license": "MIT",
       "workspaces": [
         "test/fixture-projects/*"
diff --git a/package.json b/package.json
index 4c9762e..f722b5e 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@solarity/hardhat-zkit",
-  "version": "0.4.11",
+  "version": "0.4.12",
   "description": "The ultimate TypeScript environment for Circom development",
   "main": "dist/src/index.js",
   "types": "dist/src/index.d.ts",
diff --git a/src/config/config.ts b/src/config/config.ts
index e5d05a4..6a562c8 100644
--- a/src/config/config.ts
+++ b/src/config/config.ts
@@ -14,7 +14,7 @@ const defaultConfig: ZKitConfig = {
     skipFiles: [],
     c: false,
     json: false,
-    optimization: undefined,
+    optimization: "O1",
   },
   setupSettings: {
     contributionSettings: {
diff --git a/src/types/zkit-config.ts b/src/types/zkit-config.ts
index 9cc84c2..18138b8 100644
--- a/src/types/zkit-config.ts
+++ b/src/types/zkit-config.ts
@@ -16,7 +16,7 @@ export type CompilationSettings = FileFilterSettings & {
   artifactsDir: string;
   c: boolean;
   json: boolean;
-  optimization?: "O0" | "O1" | "O2";
+  optimization: "O0" | "O1" | "O2";
 };
 
 export type SetupSettings = FileFilterSettings & {
diff --git a/test/constants.ts b/test/constants.ts
index 93899d7..84e4988 100644
--- a/test/constants.ts
+++ b/test/constants.ts
@@ -7,7 +7,7 @@ export const defaultCompileFlags: CompileFlags = {
   c: false,
   json: false,
   O0: false,
-  O1: false,
+  O1: true,
   O2: false,
 };
 
diff --git a/test/fixture-projects/hardhat-project-defined-config/hardhat.config.ts b/test/fixture-projects/hardhat-project-defined-config/hardhat.config.ts
index df96dbe..bed0556 100644
--- a/test/fixture-projects/hardhat-project-defined-config/hardhat.config.ts
+++ b/test/fixture-projects/hardhat-project-defined-config/hardhat.config.ts
@@ -8,7 +8,7 @@ const defaultConfig: HardhatUserConfig = {
     circuitsDir: "circuits",
     compilationSettings: {
       skipFiles: ["vendor"],
-      optimization: "O1",
+      optimization: "O2",
     },
     setupSettings: {
       ptauDir: "zkit/ptau",
diff --git a/test/integration/setup/config.ts b/test/integration/setup/config.ts
index dfaca8e..6790425 100644
--- a/test/integration/setup/config.ts
+++ b/test/integration/setup/config.ts
@@ -28,7 +28,7 @@ describe("config", () => {
           skipFiles: ["vendor"],
           c: false,
           json: false,
-          optimization: "O1",
+          optimization: "O2",
         },
         setupSettings: {
           contributionSettings: {
@@ -72,7 +72,7 @@ describe("config", () => {
           skipFiles: [],
           c: false,
           json: false,
-          optimization: undefined,
+          optimization: "O1",
         },
         setupSettings: {
           contributionSettings: {