diff --git a/src/octoprint/server/util/flask.py b/src/octoprint/server/util/flask.py
index b67a0908..7fe8ae34 100644
--- a/src/octoprint/server/util/flask.py
+++ b/src/octoprint/server/util/flask.py
@@ -530,7 +530,8 @@ def get_remote_address(request):
 
 
 def get_json_command_from_request(request, valid_commands):
-	if not "application/json" in request.headers["Content-Type"]:
+	content_type = request.headers.get("Content-Type", None)
+	if content_type is None or not "application/json" in content_type:
 		return None, None, make_response("Expected content-type JSON", 400)
 
 	data = request.json