diff --git a/constrain-bandwidth.js b/constrain-bandwidth.js
index 520e4af..bcc01fc 100644
--- a/constrain-bandwidth.js
+++ b/constrain-bandwidth.js
@@ -27,7 +27,7 @@ module.exports = function(value, mediaType) {
 
     // remove existing b=AS lines
     lines = lines.filter(function(line) {
-      return line.slice(0, 3) !== 'b=AS'
+      return line.slice(0, 4) !== 'b=AS'
     });
 
     // find the splice locations for the bandwidth lines
diff --git a/test/constrain-bandwidth.js b/test/constrain-bandwidth.js
index 5ccda23..9fc15f0 100644
--- a/test/constrain-bandwidth.js
+++ b/test/constrain-bandwidth.js
@@ -1,13 +1,21 @@
 var fs = require('fs');
 var test = require('tape');
 var constrainBW = require('../constrain-bandwidth');
-var baseSdp = fs.readFileSync(__dirname + '/fragments/test-answer-nocandidates.txt', 'utf8');
+var baseSdp = [
+  fs.readFileSync(__dirname + '/fragments/test-answer-nocandidates.txt', 'utf8'),
+  fs.readFileSync(__dirname + '/fragments/test-audio-video.txt', 'utf8')
+];
 var refSdp = [
-  fs.readFileSync(__dirname + '/output/constrain-bandwidth-session.txt', 'utf8')
-//   fs.readFileSync(__dirname + '/output/test-answer-addvideoice2.txt', 'utf8')
+  fs.readFileSync(__dirname + '/output/constrain-bandwidth-session.txt', 'utf8'),
+  fs.readFileSync(__dirname + '/output/constrain-bandwidth-video.txt', 'utf8')
 ];
 
 test('can add a bandwidth constraint to the session line', function(t) {
   t.plan(1);
-  t.equal(constrainBW(128)(baseSdp), refSdp[0]);
+  t.equal(constrainBW(128)(baseSdp[0]), refSdp[0]);
+});
+
+test('can replace video bandwidth constraint', function(t) {
+    t.plan(1);
+    t.equal(constrainBW(128, 'video')(baseSdp[1]), refSdp[1]);
 });
diff --git a/test/output/constrain-bandwidth-video.txt b/test/output/constrain-bandwidth-video.txt
new file mode 100644
index 0000000..b30ef9f
--- /dev/null
+++ b/test/output/constrain-bandwidth-video.txt
@@ -0,0 +1,95 @@
+v=0
+o=- 6100221552656226068 2 IN IP4 127.0.0.1
+s=-
+t=0 0
+a=group:BUNDLE audio video data
+a=msid-semantic: WMS h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R
+m=audio 9 UDP/TLS/RTP/SAVPF 111 103 104 9 0 8 106 105 13 126
+c=IN IP4 0.0.0.0
+a=rtcp:9 IN IP4 0.0.0.0
+a=ice-ufrag:iRrAkD4GFX9OersM
+a=ice-pwd:1lkz6OYbhrhmH7B53ccCeG+L
+a=fingerprint:sha-256 0C:51:8E:5F:72:72:19:00:F4:66:27:5D:EC:BA:72:5A:59:7D:D7:CB:03:50:9B:1C:F8:B6:23:5C:38:E4:22:D4
+a=setup:active
+a=mid:audio
+a=extmap:1 urn:ietf:params:rtp-hdrext:ssrc-audio-level
+a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
+a=sendrecv
+a=rtcp-mux
+a=rtpmap:111 opus/48000/2
+a=rtcp-fb:111 transport-cc
+a=fmtp:111 minptime=10;useinbandfec=1
+a=rtpmap:103 ISAC/16000
+a=rtpmap:104 ISAC/32000
+a=rtpmap:9 G722/8000
+a=rtpmap:0 PCMU/8000
+a=rtpmap:8 PCMA/8000
+a=rtpmap:106 CN/32000
+a=rtpmap:105 CN/16000
+a=rtpmap:13 CN/8000
+a=rtpmap:126 telephone-event/8000
+a=ssrc:2464355705 cname:D6daqc7p6+slHA48
+a=ssrc:2464355705 msid:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R cf956916-b2f0-4396-8e1c-ef868918c7f3
+a=ssrc:2464355705 mslabel:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R
+a=ssrc:2464355705 label:cf956916-b2f0-4396-8e1c-ef868918c7f3
+m=video 9 UDP/TLS/RTP/SAVPF 100 101 107 116 117 96 97 99 98
+b=AS:128
+c=IN IP4 0.0.0.0
+a=rtcp:9 IN IP4 0.0.0.0
+a=ice-ufrag:iRrAkD4GFX9OersM
+a=ice-pwd:1lkz6OYbhrhmH7B53ccCeG+L
+a=fingerprint:sha-256 0C:51:8E:5F:72:72:19:00:F4:66:27:5D:EC:BA:72:5A:59:7D:D7:CB:03:50:9B:1C:F8:B6:23:5C:38:E4:22:D4
+a=setup:active
+a=mid:video
+a=extmap:2 urn:ietf:params:rtp-hdrext:toffset
+a=extmap:3 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
+a=extmap:4 urn:3gpp:video-orientation
+a=sendrecv
+a=rtcp-mux
+a=rtcp-rsize
+a=rtpmap:100 VP8/90000
+a=rtcp-fb:100 ccm fir
+a=rtcp-fb:100 nack
+a=rtcp-fb:100 nack pli
+a=rtcp-fb:100 goog-remb
+a=rtcp-fb:100 transport-cc
+a=rtpmap:101 VP9/90000
+a=rtcp-fb:101 ccm fir
+a=rtcp-fb:101 nack
+a=rtcp-fb:101 nack pli
+a=rtcp-fb:101 goog-remb
+a=rtcp-fb:101 transport-cc
+a=rtpmap:107 H264/90000
+a=rtcp-fb:107 ccm fir
+a=rtcp-fb:107 nack
+a=rtcp-fb:107 nack pli
+a=rtcp-fb:107 goog-remb
+a=rtcp-fb:107 transport-cc
+a=fmtp:107 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f
+a=rtpmap:116 red/90000
+a=rtpmap:117 ulpfec/90000
+a=rtpmap:96 rtx/90000
+a=fmtp:96 apt=100
+a=rtpmap:97 rtx/90000
+a=fmtp:97 apt=101
+a=rtpmap:99 rtx/90000
+a=fmtp:99 apt=107
+a=rtpmap:98 rtx/90000
+a=fmtp:98 apt=116
+a=ssrc-group:FID 1605580382 3794581275
+a=ssrc:1605580382 cname:D6daqc7p6+slHA48
+a=ssrc:1605580382 msid:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R ef684928-5143-4e2a-9ac7-e2a4e2278e10
+a=ssrc:1605580382 mslabel:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R
+a=ssrc:1605580382 label:ef684928-5143-4e2a-9ac7-e2a4e2278e10
+a=ssrc:3794581275 cname:D6daqc7p6+slHA48
+a=ssrc:3794581275 msid:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R ef684928-5143-4e2a-9ac7-e2a4e2278e10
+a=ssrc:3794581275 mslabel:h888ZGNbE0nghXOfNtrZLUg7ZTgvc0kpMx5R
+a=ssrc:3794581275 label:ef684928-5143-4e2a-9ac7-e2a4e2278e10
+m=application 9 DTLS/SCTP 5000
+c=IN IP4 0.0.0.0
+a=ice-ufrag:iRrAkD4GFX9OersM
+a=ice-pwd:1lkz6OYbhrhmH7B53ccCeG+L
+a=fingerprint:sha-256 0C:51:8E:5F:72:72:19:00:F4:66:27:5D:EC:BA:72:5A:59:7D:D7:CB:03:50:9B:1C:F8:B6:23:5C:38:E4:22:D4
+a=setup:active
+a=mid:data
+a=sctpmap:5000 webrtc-datachannel 1024