diff --git a/lib/cmap/message_stream.js b/lib/cmap/message_stream.js
index 4c64895724..c8f458e53a 100644
--- a/lib/cmap/message_stream.js
+++ b/lib/cmap/message_stream.js
@@ -39,32 +39,7 @@ class MessageStream extends Duplex {
     const buffer = this[kBuffer];
     buffer.append(chunk);
 
-    while (buffer.length >= 4) {
-      const sizeOfMessage = buffer.readInt32LE(0);
-      if (sizeOfMessage < 0) {
-        callback(new MongoParseError(`Invalid message size: ${sizeOfMessage}`));
-        return;
-      }
-
-      if (sizeOfMessage > this.maxBsonMessageSize) {
-        callback(
-          new MongoParseError(
-            `Invalid message size: ${sizeOfMessage}, max allowed: ${this.maxBsonMessageSize}`
-          )
-        );
-        return;
-      }
-
-      if (sizeOfMessage > buffer.length) {
-        callback();
-        return;
-      }
-
-      const messageBuffer = buffer.slice(0, sizeOfMessage);
-      buffer.consume(sizeOfMessage);
-
-      processMessage(this, messageBuffer, callback);
-    }
+    processIncomingData(this, callback);
   }
 
   _read(/* size */) {
@@ -125,7 +100,36 @@ function canCompress(command) {
   return !uncompressibleCommands.has(commandName);
 }
 
-function processMessage(stream, message, callback) {
+function processIncomingData(stream, callback) {
+  const buffer = stream[kBuffer];
+  if (buffer.length < 4) {
+    callback();
+    return;
+  }
+
+  const sizeOfMessage = buffer.readInt32LE(0);
+  if (sizeOfMessage < 0) {
+    callback(new MongoParseError(`Invalid message size: ${sizeOfMessage}`));
+    return;
+  }
+
+  if (sizeOfMessage > stream.maxBsonMessageSize) {
+    callback(
+      new MongoParseError(
+        `Invalid message size: ${sizeOfMessage}, max allowed: ${stream.maxBsonMessageSize}`
+      )
+    );
+    return;
+  }
+
+  if (sizeOfMessage > buffer.length) {
+    callback();
+    return;
+  }
+
+  const message = buffer.slice(0, sizeOfMessage);
+  buffer.consume(sizeOfMessage);
+
   const messageHeader = {
     length: message.readInt32LE(0),
     requestId: message.readInt32LE(4),
@@ -142,7 +146,12 @@ function processMessage(stream, message, callback) {
       new ResponseType(stream.bson, message, messageHeader, messageBody, responseOptions)
     );
 
-    callback();
+    if (buffer.length >= 4) {
+      processIncomingData(stream, callback);
+    } else {
+      callback();
+    }
+
     return;
   }
 
@@ -176,7 +185,11 @@ function processMessage(stream, message, callback) {
       new ResponseType(stream.bson, message, messageHeader, messageBody, responseOptions)
     );
 
-    callback();
+    if (buffer.length >= 4) {
+      processIncomingData(stream, callback);
+    } else {
+      callback();
+    }
   });
 }
 
diff --git a/test/unit/cmap/message_stream.test.js b/test/unit/cmap/message_stream.test.js
index 6487dcf57e..aed67e2c4e 100644
--- a/test/unit/cmap/message_stream.test.js
+++ b/test/unit/cmap/message_stream.test.js
@@ -8,7 +8,12 @@ const expect = require('chai').expect;
 
 function bufferToStream(buffer) {
   const stream = new Readable();
-  stream.push(buffer);
+  if (Array.isArray(buffer)) {
+    buffer.forEach(b => stream.push(b));
+  } else {
+    stream.push(buffer);
+  }
+
   stream.push(null);
   return stream;
 }
@@ -24,6 +29,31 @@ describe('Message Stream', function() {
         ),
         documents: [{ ismaster: 1 }]
       },
+      {
+        description: 'valid multiple OP_REPLY',
+        expectedMessageCount: 4,
+        data: Buffer.from(
+          '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000' +
+            '370000000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000',
+          'hex'
+        ),
+        documents: [{ ismaster: 1 }]
+      },
+      {
+        description: 'valid OP_REPLY (partial)',
+        data: [
+          Buffer.from('37', 'hex'),
+          Buffer.from('0000', 'hex'),
+          Buffer.from(
+            '000100000001000000010000000000000000000000000000000000000001000000130000001069736d6173746572000100000000',
+            'hex'
+          )
+        ],
+        documents: [{ ismaster: 1 }]
+      },
+
       {
         description: 'valid OP_MSG',
         data: Buffer.from(
@@ -32,6 +62,19 @@ describe('Message Stream', function() {
         ),
         documents: [{ $db: 'admin', ismaster: 1 }]
       },
+      {
+        description: 'valid multiple OP_MSG',
+        expectedMessageCount: 4,
+        data: Buffer.from(
+          '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000' +
+            '370000000100000000000000dd0700000000000000220000001069736d6173746572000100000002246462000600000061646d696e0000',
+          'hex'
+        ),
+        documents: [{ $db: 'admin', ismaster: 1 }]
+      },
+
       {
         description: 'Invalid message size (negative)',
         data: Buffer.from('ffffffff', 'hex'),
@@ -46,10 +89,13 @@ describe('Message Stream', function() {
       it(test.description, function(done) {
         const bson = new BSON();
         const error = test.error;
+        const expectedMessageCount = test.expectedMessageCount || 1;
         const inputStream = bufferToStream(test.data);
         const messageStream = new MessageStream({ bson });
 
+        let messageCount = 0;
         messageStream.on('message', msg => {
+          messageCount++;
           if (error) {
             done(new Error(`expected error: ${error}`));
             return;
@@ -63,7 +109,9 @@ describe('Message Stream', function() {
               .that.deep.equals(test.documents);
           }
 
-          done();
+          if (messageCount === expectedMessageCount) {
+            done();
+          }
         });
 
         messageStream.on('error', err => {