diff --git a/README.md b/README.md
index cbf4163..b8bf925 100644
--- a/README.md
+++ b/README.md
@@ -51,7 +51,10 @@ ShareDrop uses WebRTC only and isn't compatible with Safari browsers. Snapdrop u
 
     # open a second shell:
     cd snapdrop/client
+    # Python 2
     python -m SimpleHTTPServer
+    # Python 3
+    python3 -m http.server
 ```
 
 Now point your browser to http://localhost:8000.
diff --git a/client/scripts/network.js b/client/scripts/network.js
index afda326..8c1ddcb 100644
--- a/client/scripts/network.js
+++ b/client/scripts/network.js
@@ -273,8 +273,12 @@ class RTCPeer extends Peer {
 
         if (message.sdp) {
             this._conn.setRemoteDescription(new RTCSessionDescription(message.sdp))
-                .then( _ => this._conn.createAnswer())
-                .then(d => this._onDescription(d))
+                .then( _ => {
+                    if (message.sdp.type === 'offer') {
+                        return this._conn.createAnswer()
+                            .then(d => this._onDescription(d));
+                    }
+                })
                 .catch(e => this._onError(e));
         } else if (message.ice) {
             this._conn.addIceCandidate(new RTCIceCandidate(message.ice));
@@ -510,4 +514,4 @@ RTCPeer.config = {
         credential: 'JZEOEt2V3Qb0y27GRntt2u2PAYA=',
         username: '28224511:1379330808'
     }]
-}
\ No newline at end of file
+}