diff --git a/src/directive.ts b/src/directive.ts
index 59caa56e..f6e13cc1 100644
--- a/src/directive.ts
+++ b/src/directive.ts
@@ -162,7 +162,7 @@ const applyArgToApiSchemaTemplate = (template: string, apiArgs: any[]): string =
     const placeholder = match[0]; // `$1`
     const idx = parseInt(match[1], 10) - 1; // start with `1 - 1`
     const apiArg = apiArgs[idx];
-    if (!apiArg) {
+    if (apiArg === undefined) {
       template = template.replace(placeholder, '');
       continue;
     }
diff --git a/tests/myzod.spec.ts b/tests/myzod.spec.ts
index 4ec29034..b4e3d827 100644
--- a/tests/myzod.spec.ts
+++ b/tests/myzod.spec.ts
@@ -539,4 +539,38 @@ describe('myzod', () => {
       }
     });
   });
+
+  it('properly generates custom directive values', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      input UserCreateInput {
+        name: String! @constraint(startsWith: "Sir")
+        age: Int! @constraint(min: 0, max: 100)
+      }
+      directive @constraint(startsWith: String, min: Int, max: Int) on INPUT_FIELD_DEFINITION
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'myzod',
+        directives: {
+          constraint: {
+            min: 'min',
+            max: 'max',
+            startsWith: ['pattern', '/^$1/'],
+          },
+        },
+      },
+      {}
+    );
+    const wantContains = [
+      // User Create Input
+      'export function UserCreateInputSchema(): myzod.Type<UserCreateInput> {',
+      'name: myzod.string().pattern(/^Sir/),',
+      'age: myzod.number().min(0).max(100)',
+    ];
+    for (const wantContain of wantContains) {
+      expect(result.content).toContain(wantContain);
+    }
+  });
 });
diff --git a/tests/yup.spec.ts b/tests/yup.spec.ts
index 975d40e8..6a8d5462 100644
--- a/tests/yup.spec.ts
+++ b/tests/yup.spec.ts
@@ -452,4 +452,38 @@ describe('yup', () => {
       }
     });
   });
+
+  it('properly generates custom directive values', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      input UserCreateInput {
+        name: String! @constraint(startsWith: "Sir")
+        age: Int! @constraint(min: 0, max: 100)
+      }
+      directive @constraint(startsWith: String, min: Int, max: Int) on INPUT_FIELD_DEFINITION
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'yup',
+        directives: {
+          constraint: {
+            min: 'min',
+            max: 'max',
+            startsWith: ['matches', '/^$1/'],
+          },
+        },
+      },
+      {}
+    );
+    const wantContains = [
+      // User Create Input
+      'export function UserCreateInputSchema(): yup.SchemaOf<UserCreateInput> {',
+      'name: yup.string().defined().matches(/^Sir/),',
+      'age: yup.number().defined().min(0).max(100)',
+    ];
+    for (const wantContain of wantContains) {
+      expect(result.content).toContain(wantContain);
+    }
+  });
 });
diff --git a/tests/zod.spec.ts b/tests/zod.spec.ts
index f9f3fe41..c48008aa 100644
--- a/tests/zod.spec.ts
+++ b/tests/zod.spec.ts
@@ -637,4 +637,38 @@ describe('zod', () => {
       }
     });
   });
+
+  it('properly generates custom directive values', async () => {
+    const schema = buildSchema(/* GraphQL */ `
+      input UserCreateInput {
+        name: String! @constraint(startsWith: "Sir")
+        age: Int! @constraint(min: 0, max: 100)
+      }
+      directive @constraint(startsWith: String, min: Int, max: Int) on INPUT_FIELD_DEFINITION
+    `);
+    const result = await plugin(
+      schema,
+      [],
+      {
+        schema: 'zod',
+        directives: {
+          constraint: {
+            min: 'min',
+            max: 'max',
+            startsWith: ['regex', '/^$1/'],
+          },
+        },
+      },
+      {}
+    );
+    const wantContains = [
+      // User Create Input
+      'export function UserCreateInputSchema(): z.ZodObject<Properties<UserCreateInput>> {',
+      'name: z.string().regex(/^Sir/),',
+      'age: z.number().min(0).max(100)',
+    ];
+    for (const wantContain of wantContains) {
+      expect(result.content).toContain(wantContain);
+    }
+  });
 });