diff --git a/tests/fixtures/migration/new_cassette.json b/tests/fixtures/migration/new_cassette.json
index 2b1bac6..5526989 100644
--- a/tests/fixtures/migration/new_cassette.json
+++ b/tests/fixtures/migration/new_cassette.json
@@ -6,9 +6,9 @@
             "request": {
                 "body": null,
                 "headers": {
-                    "Accept": ["*/*"],
-                    "Accept-Encoding": ["gzip, deflate, compress"],
-                    "User-Agent": ["python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"]
+                    "accept": ["*/*"],
+                    "accept-encoding": ["gzip, deflate, compress"],
+                    "user-agent": ["python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"]
                 },
                 "method": "GET",
                 "uri": "http://httpbin.org/ip"
diff --git a/tests/fixtures/migration/new_cassette.yaml b/tests/fixtures/migration/new_cassette.yaml
index b76eef9..e132e5a 100644
--- a/tests/fixtures/migration/new_cassette.yaml
+++ b/tests/fixtures/migration/new_cassette.yaml
@@ -3,9 +3,9 @@ interactions:
 - request:
     body: null
     headers: 
-      Accept: ['*/*']
-      Accept-Encoding: ['gzip, deflate, compress']
-      User-Agent: ['python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0']
+      accept: ['*/*']
+      accept-encoding: ['gzip, deflate, compress']
+      user-agent: ['python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0']
     method: GET
     uri: http://httpbin.org/ip
   response:
diff --git a/tests/fixtures/migration/old_cassette.json b/tests/fixtures/migration/old_cassette.json
index 22fd9cd..f6bfed1 100644
--- a/tests/fixtures/migration/old_cassette.json
+++ b/tests/fixtures/migration/old_cassette.json
@@ -5,9 +5,9 @@
             "protocol": "http", 
             "method": "GET", 
             "headers": {
-                "Accept-Encoding": "gzip, deflate, compress", 
-                "Accept": "*/*", 
-                "User-Agent": "python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"
+                "accept-encoding": "gzip, deflate, compress", 
+                "accept": "*/*", 
+                "user-agent": "python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0"
             }, 
             "host": "httpbin.org", 
             "path": "/ip", 
@@ -19,12 +19,12 @@
                 "code": 200
             }, 
             "headers": [
-                "Access-Control-Allow-Origin: *\r\n", 
-                "Content-Type: application/json\r\n", 
-                "Date: Mon, 21 Apr 2014 23:13:40 GMT\r\n", 
-                "Server: gunicorn/0.17.4\r\n", 
-                "Content-Length: 32\r\n", 
-                "Connection: keep-alive\r\n"
+                "access-control-allow-origin: *\r\n", 
+                "content-type: application/json\r\n", 
+                "date: Mon, 21 Apr 2014 23:13:40 GMT\r\n", 
+                "server: gunicorn/0.17.4\r\n", 
+                "content-length: 32\r\n", 
+                "connection: keep-alive\r\n"
             ], 
             "body": {
                 "string": "{\n  \"origin\": \"217.122.164.194\"\n}"
diff --git a/tests/fixtures/migration/old_cassette.yaml b/tests/fixtures/migration/old_cassette.yaml
index 970823d..cd1eacb 100644
--- a/tests/fixtures/migration/old_cassette.yaml
+++ b/tests/fixtures/migration/old_cassette.yaml
@@ -1,9 +1,9 @@
 - request: !!python/object:vcr.request.Request
     body: null
     headers: !!python/object/apply:__builtin__.frozenset
-    - - !!python/tuple [Accept-Encoding, 'gzip, deflate, compress']
-      - !!python/tuple [User-Agent, python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0]
-      - !!python/tuple [Accept, '*/*']
+    - - !!python/tuple [accept-encoding, 'gzip, deflate, compress']
+      - !!python/tuple [user-agent, python-requests/2.2.1 CPython/2.6.1 Darwin/10.8.0]
+      - !!python/tuple [accept, '*/*']
     host: httpbin.org
     method: GET
     path: /ip
@@ -11,8 +11,8 @@
     protocol: http
   response:
     body: {string: !!python/unicode "{\n  \"origin\": \"217.122.164.194\"\n}"}
-    headers: [!!python/unicode "Access-Control-Allow-Origin: *\r\n", !!python/unicode "Content-Type:
-        application/json\r\n", !!python/unicode "Date: Mon, 21 Apr 2014 23:06:09 GMT\r\n",
-      !!python/unicode "Server: gunicorn/0.17.4\r\n", !!python/unicode "Content-Length:
-        32\r\n", !!python/unicode "Connection: keep-alive\r\n"]
+    headers: [!!python/unicode "access-control-allow-origin: *\r\n", !!python/unicode "content-type:
+        application/json\r\n", !!python/unicode "date: Mon, 21 Apr 2014 23:06:09 GMT\r\n",
+      !!python/unicode "server: gunicorn/0.17.4\r\n", !!python/unicode "content-length:
+        32\r\n", !!python/unicode "connection: keep-alive\r\n"]
     status: {code: 200, message: OK}