--- a/scheduler.py
+++ b/scheduler.py
@@ -299,17 +299,17 @@ class TriggerBouncerCheck(Triggerable):
         log.msg('%s: polling' % self.__class__.__name__)
         bouncerProductName = self.release_config.get('bouncerProductName') or \
             self.release_config.get('productName').capitalize()
         version = self.release_config.get('version')
         partialVersions = []
         if self.appendBuildNumber:
             version += 'build%s' % self.release_config.get('buildNumber')
             for partialVersion, info in self.release_config.get("partialUpdates").iteritems():
-                partialVersions.append("%sbuild%s" % partialVersion, info["buildNumber"])
+                partialVersions.append("%sbuild%s" % (partialVersion, info["buildNumber"]))
         if not partialVersions:
             partialVersions = self.release_config.get("partialUpdates").keys()
         d = get_release_uptake(
             tuxedoServerUrl=self.release_config.get('tuxedoServerUrl'),
             bouncerProductName=bouncerProductName,
             version=version,
             platforms=self.release_config.get('enUSPlatforms'),
             partialVersions=partialVersions,