Index: src/main/java/info/magnolia/cms/beans/config/MIMEMapping.java
===================================================================
--- src/main/java/info/magnolia/cms/beans/config/MIMEMapping.java	(revision 3135)
+++ src/main/java/info/magnolia/cms/beans/config/MIMEMapping.java	(working copy)
@@ -203,7 +203,8 @@
         }
 
         if (StringUtils.isNotEmpty(extension)) {
-            log.info("Cannot find MIME type for extension \"{}\"", extension);
+            log.info("Cannot find MIME type for extension \"{}\". Falling back to binary default.", extension);
+            return("application/octet-stream");
         }
 
         final String defaultExtension = ServerConfiguration.getInstance().getDefaultExtension();