diff --git a/src/octoprint/plugins/softwareupdate/__init__.py b/src/octoprint/plugins/softwareupdate/__init__.py
index 4c2a16ad..a503f832 100644
--- a/src/octoprint/plugins/softwareupdate/__init__.py
+++ b/src/octoprint/plugins/softwareupdate/__init__.py
@@ -766,7 +766,7 @@ class SoftwareUpdatePlugin(octoprint.plugin.BlueprintPlugin,
 			else:
 				result["current"] = VERSION
 
-				if check["type"] == "github_release" and (check["prerelease"] or BRANCH != stable_branch):
+				if check["type"] == "github_release" and (check.get("prerelease", None) or BRANCH != stable_branch):
 					# we are tracking github releases and are either also tracking prerelease OR are currently installed
 					# from something that is not the stable (master) branch => we need to change some parameters