diff --git a/packages/taco/src/conditions/sequential.ts b/packages/taco/src/conditions/sequential.ts
index ae45bc2d..2f996eb2 100644
--- a/packages/taco/src/conditions/sequential.ts
+++ b/packages/taco/src/conditions/sequential.ts
@@ -36,6 +36,25 @@ export const sequentialConditionSchema: z.ZodSchema = baseConditionSchema
       message: 'Exceeded max nested depth of 2 for multi-condition type',
       path: ['conditionVariables'],
     }, // Max nested depth of 2
+  )
+  .refine(
+    // check for duplicate var names
+    (condition) => {
+      const seen = new Set();
+      return condition.conditionVariables.every(
+        (child: ConditionVariableProps) => {
+          if (seen.has(child.varName)) {
+            return false;
+          }
+          seen.add(child.varName);
+          return true;
+        },
+      );
+    },
+    {
+      message: 'Duplicate variable names are not allowed',
+      path: ['conditionVariables'],
+    },
   );
 
 export type ConditionVariableProps = z.infer<typeof conditionVariableSchema>;
diff --git a/packages/taco/test/conditions/sequential.test.ts b/packages/taco/test/conditions/sequential.test.ts
index 1fde2859..08ad8397 100644
--- a/packages/taco/test/conditions/sequential.test.ts
+++ b/packages/taco/test/conditions/sequential.test.ts
@@ -62,6 +62,33 @@ describe('validation', () => {
     });
   });
 
+  it('rejects duplication variable names', () => {
+    const result = SequentialCondition.validate(sequentialConditionSchema, {
+      conditionVariables: [
+        {
+          varName: 'var1',
+          condition: testRpcConditionObj,
+        },
+        {
+          varName: 'var2',
+          condition: testTimeConditionObj,
+        },
+        {
+          varName: 'var1',
+          condition: testContractConditionObj,
+        },
+      ],
+    });
+
+    expect(result.error).toBeDefined();
+    expect(result.data).toBeUndefined();
+    expect(result.error?.format()).toMatchObject({
+      conditionVariables: {
+        _errors: ['Duplicate variable names are not allowed'],
+      },
+    });
+  });
+
   it('rejects > max number of condition variables', () => {
     const tooManyConditionVariables = new Array(6);
     for (let i = 0; i < tooManyConditionVariables.length; i++) {
@@ -78,7 +105,7 @@ describe('validation', () => {
     expect(result.data).toBeUndefined();
     expect(result.error?.format()).toMatchObject({
       conditionVariables: {
-        _errors: [`Array must contain at most 5 element(s)`],
+        _errors: ['Array must contain at most 5 element(s)'],
       },
     });
   });