diff --git a/owslib/map/wms130.py b/owslib/map/wms130.py
index <HASH>..<HASH> 100644
--- a/owslib/map/wms130.py
+++ b/owslib/map/wms130.py
@@ -665,9 +665,11 @@ class ContentMetadata(AbstractContentMetadata):
         self.dataUrls = []
         for m in elem.findall(nspath('DataURL', WMS_NAMESPACE)):
             dataUrl = {
-                'format': m.find(nspath('Format', WMS_NAMESPACE)).text.strip(),
+                'format': m.find(nspath('Format', WMS_NAMESPACE)).text,
                 'url': m.find(nspath('OnlineResource', WMS_NAMESPACE)).attrib['{http://www.w3.org/1999/xlink}href']
             }
+            if dataUrl['format'] is not None:
+                dataUrl['format'] = dataUrl['format'].strip()
             self.dataUrls.append(dataUrl)
 
         # FeatureListURLs
Handle empty DataURL element in GetCapabilities

As per the specification, the DataURL element may be empty. Using strip() on a empty string raises an exception. This was dealt with in the code for <I> but not for <I>.