diff --git a/readthedocs/proxito/tests/responses/v0.json b/readthedocs/proxito/tests/responses/v0.json
index 07f2f57c268..2f15aaf25c8 100644
--- a/readthedocs/proxito/tests/responses/v0.json
+++ b/readthedocs/proxito/tests/responses/v0.json
@@ -1,4 +1,5 @@
 {
+  "api_version": "0",
   "comment": "THIS RESPONSE IS IN ALPHA FOR TEST PURPOSES ONLY AND IT'S GOING TO CHANGE COMPLETELY -- DO NOT USE IT!",
   "projects": {
     "current": {
diff --git a/readthedocs/proxito/tests/responses/v1.json b/readthedocs/proxito/tests/responses/v1.json
index 21a1c1b6dfb..b61cf11cfdc 100644
--- a/readthedocs/proxito/tests/responses/v1.json
+++ b/readthedocs/proxito/tests/responses/v1.json
@@ -1,3 +1,4 @@
 {
+    "api_version": "1",
     "comment": "Undefined yet. Use v0 for now"
 }
diff --git a/readthedocs/proxito/views/hosting.py b/readthedocs/proxito/views/hosting.py
index 4a7725b56e4..90788fd7225 100644
--- a/readthedocs/proxito/views/hosting.py
+++ b/readthedocs/proxito/views/hosting.py
@@ -244,6 +244,7 @@ def _v0(self, project, version, build, filename, user):
         project_features = project.features.all().values_list("feature_id", flat=True)
 
         data = {
+            "api_version": "0",
             "comment": (
                 "THIS RESPONSE IS IN ALPHA FOR TEST PURPOSES ONLY"
                 " AND IT'S GOING TO CHANGE COMPLETELY -- DO NOT USE IT!"
@@ -432,6 +433,7 @@ def _v0(self, project, version, build, filename, user):
 
     def _v1(self, project, version, build, filename, user):
         return {
+            "api_version": "1",
             "comment": "Undefined yet. Use v0 for now",
         }