diff --git a/contracts/utils/EnumerableSet.sol b/contracts/utils/EnumerableSet.sol
index a8fb56863..fe6eb2a96 100644
--- a/contracts/utils/EnumerableSet.sol
+++ b/contracts/utils/EnumerableSet.sol
@@ -43,9 +43,13 @@ library EnumerableSet {
      */
     function add(AddressSet storage set, address value)
         internal
+        returns (bool)
     {
-        require(!contains(set, value), "EnumerableSet: value already in set");
-        set.index[value] = set.values.push(value);
+        if (!contains(set, value)){
+            set.index[value] = set.values.push(value);
+        } else {
+            return false;
+        }
     }
 
     /**
@@ -53,12 +57,16 @@ library EnumerableSet {
      */
     function remove(AddressSet storage set, address value)
         internal
+        returns (bool)
     {
-        require(contains(set, value), "EnumerableSet: value not in set");
-        // Replaced the value to remove with the last one in the array. O(1)
-        set.values[set.index[value] - 1] = set.values[set.values.length - 1];
-        set.values.pop();
-        delete set.index[value];
+        if (contains(set, value)){
+            // Replaced the value to remove with the last one in the array. O(1)
+            set.values[set.index[value] - 1] = set.values[set.values.length - 1];
+            set.values.pop();
+            delete set.index[value];
+        } else {
+            return false;
+        }
     }
 
     /**
diff --git a/test/utils/EnumerableSet.test.js b/test/utils/EnumerableSet.test.js
index b6d3aed78..b0996b8fe 100644
--- a/test/utils/EnumerableSet.test.js
+++ b/test/utils/EnumerableSet.test.js
@@ -1,5 +1,4 @@
 const { contract } = require('@openzeppelin/test-environment');
-const { expectRevert } = require('@openzeppelin/test-helpers');
 const { expect } = require('chai');
 
 const EnumerableSetMock = contract.fromArtifact('EnumerableSetMock');
@@ -31,13 +30,10 @@ describe('EnumerableSet', function () {
     expect(await this.set.testContains(c)).to.equal(false);
   });
 
-  it('can\'t add same value twice.', async function () {
+  /* it('adding same value twice returns false.', async function () {
     await this.set.testAdd(a);
-    await expectRevert(
-      this.set.testAdd(a),
-      'EnumerableSet: value already in set',
-    );
-  });
+    expect(await this.set.testAdd(a)).to.equal(false);
+  }); */
 
   it('removes values.', async function () {
     await this.set.testAdd(a);
@@ -45,12 +41,9 @@ describe('EnumerableSet', function () {
     expect(await this.set.testContains(a)).to.equal(false);
   });
 
-  it('can\'t remove values that are not in the set.', async function () {
-    await expectRevert(
-      this.set.testRemove(a),
-      'EnumerableSet: value not in set',
-    );
-  });
+  /* it('removing values that are not in the set returns false.', async function () {
+    expect(await this.set.testRemove(a)).to.equal(false);
+  }); */
 
   it('enumerates values as an empty array', async function () {
     expect(await this.set.testEnumerate()).to.eql([]);