diff --git a/src/pylorax/api/errors.py b/src/pylorax/api/errors.py
index e2be52c6..c4edfe7b 100644
--- a/src/pylorax/api/errors.py
+++ b/src/pylorax/api/errors.py
@@ -32,5 +32,8 @@ INVALID_NAME = "InvalidName"
 # Returned from the API when a blueprint that was requested does not exist.
 UNKNOWN_BLUEPRINT = "UnknownBlueprint"
 
+# Returned from the API when a commit that was requested does not exist.
+UNKNOWN_COMMIT = "UnknownCommit"
+
 # Returned from the API when a UUID that was requested does not exist.
 UNKNOWN_UUID = "UnknownUUID"
diff --git a/src/pylorax/api/v0.py b/src/pylorax/api/v0.py
index 9564e646..b0d43b2f 100644
--- a/src/pylorax/api/v0.py
+++ b/src/pylorax/api/v0.py
@@ -1269,7 +1269,7 @@ def v0_api(api):
                 workspace_write(api.config["GITLOCK"].repo, branch, blueprint)
         except Exception as e:
             log.error("(v0_blueprints_undo) %s", str(e))
-            return jsonify(status=False, errors=[str(e)]), 400
+            return jsonify(status=False, errors=[{"id": UNKNOWN_COMMIT, "msg": str(e)}]), 400
         else:
             return jsonify(status=True)
 
@@ -1322,7 +1322,7 @@ def v0_api(api):
                     old_blueprint = read_recipe_commit(api.config["GITLOCK"].repo, branch, blueprint_name, from_commit)
         except Exception as e:
             log.error("(v0_blueprints_diff) %s", str(e))
-            return jsonify(status=False, errors=[str(e)]), 400
+            return jsonify(status=False, errors=[{"id": UNKNOWN_COMMIT, "msg": str(e)}]), 400
 
         try:
             if to_commit == "WORKSPACE":
@@ -1340,7 +1340,7 @@ def v0_api(api):
                     new_blueprint = read_recipe_commit(api.config["GITLOCK"].repo, branch, blueprint_name, to_commit)
         except Exception as e:
             log.error("(v0_blueprints_diff) %s", str(e))
-            return jsonify(status=False, errors=[str(e)]), 400
+            return jsonify(status=False, errors=[{"id": UNKNOWN_COMMIT, "msg": str(e)}]), 400
 
         diff = recipe_diff(old_blueprint, new_blueprint)
         return jsonify(diff=diff)