diff --git a/fdroidserver/common.py b/fdroidserver/common.py
index 4772abc8..0463db29 100644
--- a/fdroidserver/common.py
+++ b/fdroidserver/common.py
@@ -157,7 +157,7 @@ def fill_config_defaults(thisconfig):
                         thisconfig['java_paths'][m.group(1)] = d
 
     for java_version in ('7', '8', '9'):
-        if not java_version in thisconfig['java_paths']:
+        if java_version not in thisconfig['java_paths']:
             continue
         java_home = thisconfig['java_paths'][java_version]
         jarsigner = os.path.join(java_home, 'bin', 'jarsigner')
diff --git a/fdroidserver/signindex.py b/fdroidserver/signindex.py
index 82f2216a..1d0c3200 100644
--- a/fdroidserver/signindex.py
+++ b/fdroidserver/signindex.py
@@ -40,7 +40,7 @@ def main():
 
     config = common.read_config(options)
 
-    if not 'jarsigner' in config:
+    if 'jarsigner' not in config:
         logging.critical('Java jarsigner not found! Install in standard location or set java_paths!')
         sys.exit(1)