diff --git a/cowrie/output/jsonlog.py b/cowrie/output/jsonlog.py
index d1d2df6..e1ae924 100644
--- a/cowrie/output/jsonlog.py
+++ b/cowrie/output/jsonlog.py
@@ -49,7 +49,7 @@ class Output(cowrie.core.output.Output):
         self.outfile.close()
 
     def write(self, logentry):
-        for i in logentry.keys():
+        for i in list(logentry.keys()):
             # remove twisted 15 legacy keys
             if i.startswith('log_'):
                 del logentry[i]
diff --git a/cowrie/output/splunk.py b/cowrie/output/splunk.py
index bcb56e5..acacd91 100644
--- a/cowrie/output/splunk.py
+++ b/cowrie/output/splunk.py
@@ -36,7 +36,7 @@ class Output(cowrie.core.output.Output):
         pass
 
     def write(self, logentry):
-        for i in logentry.keys():
+        for i in list(logentry.keys()):
             # remove twisted 15 legacy keys
             if i.startswith('log_'):
                 del logentry[i]