diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 5955590..4ad5aeb 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -52,7 +52,7 @@ jobs:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        node: [^18, ^20]
+        node: [^20]
     steps:
       - uses: actions/checkout@v3
 
diff --git a/.github/workflows/platform_test.yml b/.github/workflows/platform_test.yml
index 9f4d21f..c184851 100644
--- a/.github/workflows/platform_test.yml
+++ b/.github/workflows/platform_test.yml
@@ -11,7 +11,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [^18, ^20]
+        node-version: [^20]
     steps:
       - uses: actions/checkout@v3
 
@@ -37,7 +37,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [^18, ^20]
+        node-version: [^20]
     steps:
       - uses: actions/checkout@v3
 
@@ -60,7 +60,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        node-version: [^18, ^20]
+        node-version: [^20]
     steps:
       - uses: actions/checkout@v3
 
diff --git a/src/internalEnforcer.ts b/src/internalEnforcer.ts
index 6787601..ac74f0a 100644
--- a/src/internalEnforcer.ts
+++ b/src/internalEnforcer.ts
@@ -33,7 +33,7 @@ export class InternalEnforcer extends CoreEnforcer {
       try {
         await this.adapter.addPolicy(sec, ptype, rule);
       } catch (e) {
-        if (e.message !== 'not implemented') {
+        if (!(e instanceof Error) || e.message !== 'not implemented') {
           throw e;
         }
       }
@@ -70,7 +70,7 @@ export class InternalEnforcer extends CoreEnforcer {
         try {
           await (this.adapter as BatchAdapter).addPolicies(sec, ptype, rules);
         } catch (e) {
-          if (e.message !== 'not implemented') {
+          if (!(e instanceof Error) || e.message !== 'not implemented') {
             throw e;
           }
         }
@@ -108,7 +108,7 @@ export class InternalEnforcer extends CoreEnforcer {
         try {
           await (this.adapter as UpdatableAdapter).updatePolicy(sec, ptype, oldRule, newRule);
         } catch (e) {
-          if (e.message !== 'not implemented') {
+          if (!(e instanceof Error) || e.message !== 'not implemented') {
             throw e;
           }
         }
@@ -144,7 +144,7 @@ export class InternalEnforcer extends CoreEnforcer {
       try {
         await this.adapter.removePolicy(sec, ptype, rule);
       } catch (e) {
-        if (e.message !== 'not implemented') {
+        if (!(e instanceof Error) || e.message !== 'not implemented') {
           throw e;
         }
       }
@@ -179,7 +179,7 @@ export class InternalEnforcer extends CoreEnforcer {
         try {
           await (this.adapter as BatchAdapter).removePolicies(sec, ptype, rules);
         } catch (e) {
-          if (e.message !== 'not implemented') {
+          if (!(e instanceof Error) || e.message !== 'not implemented') {
             throw e;
           }
         }
@@ -212,7 +212,7 @@ export class InternalEnforcer extends CoreEnforcer {
       try {
         await this.adapter.removeFilteredPolicy(sec, ptype, fieldIndex, ...fieldValues);
       } catch (e) {
-        if (e.message !== 'not implemented') {
+        if (!(e instanceof Error) || e.message !== 'not implemented') {
           throw e;
         }
       }
diff --git a/src/util/util.ts b/src/util/util.ts
index d2105cf..d911074 100644
--- a/src/util/util.ts
+++ b/src/util/util.ts
@@ -213,9 +213,9 @@ function policyStringToArray(policy: string): string[][] {
 
 function customIn(a: number | string, b: number | string): number {
   if ((b as any) instanceof Array) {
-    return (((b as any) as Array<any>).includes(a) as unknown) as number;
+    return (b as any as Array<any>).includes(a) as unknown as number;
   }
-  return ((a in (b as any)) as unknown) as number;
+  return (a in (b as any)) as unknown as number;
 }
 
 function bracketCompatible(exp: string): string {
diff --git a/test/enforcer.test.ts b/test/enforcer.test.ts
index 1abb1fe..36e97ab 100644
--- a/test/enforcer.test.ts
+++ b/test/enforcer.test.ts
@@ -573,9 +573,9 @@ test('test ABAC multiple eval()', async () => {
   );
 
   const e = await newEnforcer(m, policy);
-  await testEnforce(e, 56, (98 as unknown) as string, 'read', true);
-  await testEnforce(e, 23, (67 as unknown) as string, 'read', false);
-  await testEnforce(e, 78, (34 as unknown) as string, 'read', false);
+  await testEnforce(e, 56, 98 as unknown as string, 'read', true);
+  await testEnforce(e, 23, 67 as unknown as string, 'read', false);
+  await testEnforce(e, 78, 34 as unknown as string, 'read', false);
 });
 
 test('TestEnforceSync', async () => {
@@ -645,9 +645,9 @@ test('test ABAC multiple eval()', async () => {
   );
 
   const e = await newEnforcer(m, policy);
-  await testEnforce(e, 56, (98 as unknown) as string, 'read', true);
-  await testEnforce(e, 23, (67 as unknown) as string, 'read', false);
-  await testEnforce(e, 78, (34 as unknown) as string, 'read', false);
+  await testEnforce(e, 56, 98 as unknown as string, 'read', true);
+  await testEnforce(e, 23, 67 as unknown as string, 'read', false);
+  await testEnforce(e, 78, 34 as unknown as string, 'read', false);
 });
 
 test('TestBatchEnforce', async () => {
diff --git a/test/model/model.test.ts b/test/model/model.test.ts
index 7c8f028..19e2204 100644
--- a/test/model/model.test.ts
+++ b/test/model/model.test.ts
@@ -56,8 +56,9 @@ test('TestLoadModelFromConfig', (done) => {
     }
 
     if (e instanceof Error) {
+      const errorMessage = e.message;
       requiredSections.forEach((n) => {
-        if (!e.message.includes(n)) {
+        if (!errorMessage.includes(n)) {
           throw new Error(`section name: ${sectionNameMap[n]} should be in message`);
         }
       });