diff --git a/cloudinit/sources/DataSourceEc2.py b/cloudinit/sources/DataSourceEc2.py
index 41367a8b..88d4a0c3 100644
--- a/cloudinit/sources/DataSourceEc2.py
+++ b/cloudinit/sources/DataSourceEc2.py
@@ -297,11 +297,12 @@ class DataSourceEc2(sources.DataSource):
 
         result = None
         net_md = self.metadata.get('network')
-        if isinstance(net_md, dict):
+        try:
             result = convert_ec2_metadata_network_config(net_md)
-        else:
-            LOG.warning("unexpected metadata 'network' key not valid: %s",
-                        net_md)
+        except ValueError as e:
+            LOG.warning("Failed converting metadata (%s). network config=%s",
+                        e, net_md)
+
         self._network_config = result
 
         return self._network_config
@@ -470,10 +471,21 @@ def convert_ec2_metadata_network_config(network_md, macs_to_nics=None):
 
     @return A dict of network config version 1 based on the metadata and macs.
     """
-    netcfg = {'version': 1, 'config': []}
+    if not isinstance(network_md, dict):
+        raise ValueError("network_md is not a dict")
+
+    if not isinstance(network_md.get('interfaces'), dict):
+        raise ValueError("network_md had non-dict at 'interfaces'")
+
+    if not isinstance(network_md['interfaces'].get('macs'), dict):
+        raise ValueError("network_md['interfaces'] had non-dict at 'macs'")
+
+    macs_metadata = network_md['interfaces']['macs']
+
     if not macs_to_nics:
         macs_to_nics = net.get_interfaces_by_mac()
-    macs_metadata = network_md['interfaces']['macs']
+
+    netcfg = {'version': 1, 'config': []}
     for mac, nic_name in macs_to_nics.items():
         nic_metadata = macs_metadata.get(mac)
         if not nic_metadata: