diff --git a/tests/src/tests/database/ref/issueSpecificTests.js b/tests/src/tests/database/ref/issueSpecificTests.js
index 9abbb868..a1afbd78 100644
--- a/tests/src/tests/database/ref/issueSpecificTests.js
+++ b/tests/src/tests/database/ref/issueSpecificTests.js
@@ -1,4 +1,6 @@
 import should from 'should';
+import sinon from 'sinon';
+import 'should-sinon';
 import DatabaseContents from '../../support/DatabaseContents';
 
 function issueTests({ describe, it, context, firebase }) {
@@ -81,6 +83,190 @@ function issueTests({ describe, it, context, firebase }) {
       });
     });
   });
+
+  describe('issue_521', () => {
+    context('orderByChild (numerical field) and limitToLast', () => {
+      it('once() returns correct results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521');
+        // Test
+
+        return ref
+          .orderByChild('number')
+          .limitToLast(2)
+          .once('value')
+          .then((snapshot) => {
+            const val = snapshot.val();
+            // Assertion
+            val.key2.should.eql(DatabaseContents.ISSUES[521].key2);
+            val.key3.should.eql(DatabaseContents.ISSUES[521].key3);
+            should.equal(Object.keys(val).length, 2);
+
+            return Promise.resolve();
+          });
+      });
+
+      it('on() returns correct initial results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521').orderByChild('number').limitToLast(2);
+        const callback = sinon.spy();
+
+        // Test
+
+        await new Promise((resolve) => {
+          ref.on('value', (snapshot) => {
+            callback(snapshot.val());
+            resolve();
+          });
+        });
+
+        callback.should.be.calledWith({
+          key2: DatabaseContents.ISSUES[521].key2,
+          key3: DatabaseContents.ISSUES[521].key3,
+        });
+        callback.should.be.calledOnce();
+
+        return Promise.resolve();
+      });
+
+      it('on() returns correct subsequent results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521').orderByChild('number').limitToLast(2);
+        const callback = sinon.spy();
+
+        // Test
+
+        await new Promise((resolve) => {
+          ref.on('value', (snapshot) => {
+            callback(snapshot.val());
+            resolve();
+          });
+        });
+
+        callback.should.be.calledWith({
+          key2: DatabaseContents.ISSUES[521].key2,
+          key3: DatabaseContents.ISSUES[521].key3,
+        });
+        callback.should.be.calledOnce();
+
+        const newDataValue = {
+          name: 'Item 4',
+          number: 4,
+          string: 'item4',
+        };
+        const newRef = firebase.native.database().ref('tests/issues/521/key4');
+        await newRef.set(newDataValue);
+
+        await new Promise((resolve) => {
+          setTimeout(() => resolve(), 5);
+        });
+
+        // Assertions
+
+        callback.should.be.calledWith({
+          key3: DatabaseContents.ISSUES[521].key3,
+          key4: newDataValue,
+        });
+        callback.should.be.calledTwice();
+
+        return Promise.resolve();
+      });
+    });
+
+    context('orderByChild (string field) and limitToLast', () => {
+      it('once() returns correct results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521');
+        // Test
+
+        return ref
+          .orderByChild('string')
+          .limitToLast(2)
+          .once('value')
+          .then((snapshot) => {
+            const val = snapshot.val();
+            // Assertion
+            val.key2.should.eql(DatabaseContents.ISSUES[521].key2);
+            val.key3.should.eql(DatabaseContents.ISSUES[521].key3);
+            should.equal(Object.keys(val).length, 2);
+
+            return Promise.resolve();
+          });
+      });
+
+      it('on() returns correct initial results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521').orderByChild('string').limitToLast(2);
+        const callback = sinon.spy();
+
+        // Test
+
+        await new Promise((resolve) => {
+          ref.on('value', (snapshot) => {
+            callback(snapshot.val());
+            resolve();
+          });
+        });
+
+        callback.should.be.calledWith({
+          key2: DatabaseContents.ISSUES[521].key2,
+          key3: DatabaseContents.ISSUES[521].key3,
+        });
+        callback.should.be.calledOnce();
+
+        return Promise.resolve();
+      });
+
+      it('on() returns correct subsequent results', async () => {
+        // Setup
+
+        const ref = firebase.native.database().ref('tests/issues/521').orderByChild('string').limitToLast(2);
+        const callback = sinon.spy();
+
+        // Test
+
+        await new Promise((resolve) => {
+          ref.on('value', (snapshot) => {
+            callback(snapshot.val());
+            resolve();
+          });
+        });
+
+        callback.should.be.calledWith({
+          key2: DatabaseContents.ISSUES[521].key2,
+          key3: DatabaseContents.ISSUES[521].key3,
+        });
+        callback.should.be.calledOnce();
+
+        const newDataValue = {
+          name: 'Item 4',
+          number: 4,
+          string: 'item4',
+        };
+        const newRef = firebase.native.database().ref('tests/issues/521/key4');
+        await newRef.set(newDataValue);
+
+        await new Promise((resolve) => {
+          setTimeout(() => resolve(), 5);
+        });
+
+        // Assertions
+
+        callback.should.be.calledWith({
+          key3: DatabaseContents.ISSUES[521].key3,
+          key4: newDataValue,
+        });
+        callback.should.be.calledTwice();
+
+        return Promise.resolve();
+      });
+    });
+  });
 }
 
 export default issueTests;
diff --git a/tests/src/tests/support/DatabaseContents.js b/tests/src/tests/support/DatabaseContents.js
index a4a913c9..bace7f99 100644
--- a/tests/src/tests/support/DatabaseContents.js
+++ b/tests/src/tests/support/DatabaseContents.js
@@ -91,5 +91,24 @@ export default {
         uid: 'aNYxLexOb2WsXGOPiEAu47q5bxH3',
       },
     },
+
+    // https://github.com/invertase/react-native-firebase/issues/521
+    521: {
+      key1: {
+        name: 'Item 1',
+        number: 1,
+        string: 'item1',
+      },
+      key3: {
+        name: 'Item 3',
+        number: 3,
+        string: 'item3',
+      },
+      key2: {
+        name: 'Item 2',
+        number: 2,
+        string: 'item2',
+      },
+    },
   },
 };