diff --git a/index.js b/index.js
index 8ad2bdc..3d9888d 100644
--- a/index.js
+++ b/index.js
@@ -1504,6 +1504,11 @@ var collectionOperationsMap = {
       var err = ShareDbMongo.malformedQueryOperatorError('$mapReduce');
       return cb(err);
     }
+    // This function was removed in mongodb5:
+    // https://github.com/mongodb/node-mongodb-native/pull/3511
+    if (typeof collection.mapReduce !== 'function') {
+      var err = ShareDbMongo.$mapReduceDisabledError();
+    }
     var mapReduceOptions = {
       query: query,
       out: {inline: 1},
diff --git a/package.json b/package.json
index 03f9ad3..3183708 100644
--- a/package.json
+++ b/package.json
@@ -4,7 +4,7 @@
   "description": "MongoDB database adapter for ShareDB",
   "main": "index.js",
   "dependencies": {
-    "mongodb": "^2.1.2 || ^3.1.13 || ^4.0.0",
+    "mongodb": "^2.1.2 || ^3.1.13 || ^4.0.0 || ^5.0.0",
     "sharedb": "^1.9.1 || ^2.0.0 || ^3.0.0"
   },
   "devDependencies": {
@@ -16,6 +16,7 @@
     "mongodb2": "npm:mongodb@^2.1.2",
     "mongodb3": "npm:mongodb@^3.0.0",
     "mongodb4": "npm:mongodb@^4.0.0",
+    "mongodb5": "npm:mongodb@^5.0.0",
     "nyc": "^14.1.1",
     "ot-json1": "^1.0.1",
     "sharedb-mingo-memory": "^1.1.1",
@@ -29,7 +30,8 @@
     "test:mongodb2": "_SHAREDB_MONGODB_DRIVER=mongodb2 npm test",
     "test:mongodb3": "_SHAREDB_MONGODB_DRIVER=mongodb3 npm test",
     "test:mongodb4": "_SHAREDB_MONGODB_DRIVER=mongodb4 npm test",
-    "test:all": "npm run test:mongodb2 && npm run test:mongodb3 && npm run test:mongodb4",
+    "test:mongodb5": "_SHAREDB_MONGODB_DRIVER=mongodb5 npm test",
+    "test:all": "npm run test:mongodb2 && npm run test:mongodb3 && npm run test:mongodb4 && npm run test:mongodb5",
     "test-cover": "nyc --temp-dir=coverage -r text -r lcov npm run test:all"
   },
   "repository": "git://github.com/share/sharedb-mongo.git",
diff --git a/test/test_mongo.js b/test/test_mongo.js
index c288633..40d0e4a 100644
--- a/test/test_mongo.js
+++ b/test/test_mongo.js
@@ -334,6 +334,11 @@ describe('mongo db', function() {
     });
 
     it('$mapReduce queries should work when allowJavaScriptQuery == true', function(done) {
+      if (process.env._SHAREDB_MONGODB_DRIVER === 'mongodb5') {
+        // This function was removed in mongodb5:
+        // https://github.com/mongodb/node-mongodb-native/pull/3511
+        return done();
+      }
       var snapshots = [
         {type: 'json0', v: 1, data: {player: 'a', round: 1, score: 5}},
         {type: 'json0', v: 1, data: {player: 'a', round: 2, score: 7}},