diff --git a/doc/source/aws.rst b/doc/source/aws.rst
index 71a61c9da..6f81989a0 100644
--- a/doc/source/aws.rst
+++ b/doc/source/aws.rst
@@ -343,6 +343,9 @@ Selecting the ``aws`` driver adds the following options to the
 
          The username that should be used when connecting to the node.
 
+         .. warning:: This option is deprecated.  Specify the username
+                      on the diskimage definition itself instead.
+
       .. attr:: connection-type
          :type: string
 
diff --git a/doc/source/azure.rst b/doc/source/azure.rst
index 91bb47186..d80e69f86 100644
--- a/doc/source/azure.rst
+++ b/doc/source/azure.rst
@@ -510,6 +510,9 @@ section of the configuration.
 
          The username that should be used when connecting to the node.
 
+         .. warning:: This option is deprecated.  Specify the username
+                      on the diskimage definition itself instead.
+
       .. attr:: key
          :type: str
 
diff --git a/nodepool/driver/aws/config.py b/nodepool/driver/aws/config.py
index 997d3f283..93475bedb 100644
--- a/nodepool/driver/aws/config.py
+++ b/nodepool/driver/aws/config.py
@@ -94,7 +94,7 @@ class AwsProviderDiskImage(ConfigValue):
         self.pause = bool(image.get('pause', False))
         self.python_path = image.get('python-path', 'auto')
         self.shell_type = image.get('shell-type')
-        self.username = image.get('username')
+        self.username = image.get('username', diskimage.username)
         self.connection_type = image.get('connection-type', 'ssh')
         self.connection_port = image.get(
             'connection-port',
diff --git a/nodepool/driver/azure/config.py b/nodepool/driver/azure/config.py
index 6df99b177..7a8761239 100644
--- a/nodepool/driver/azure/config.py
+++ b/nodepool/driver/azure/config.py
@@ -121,7 +121,7 @@ class AzureProviderDiskImage(ConfigValue):
         self.pause = bool(image.get('pause', False))
         self.python_path = image.get('python-path', 'auto')
         self.shell_type = image.get('shell-type')
-        self.username = image.get('username')
+        self.username = image.get('username', diskimage.username)
         self.password = image.get('password')
         self.generate_password = image.get('generate-password', False)
         self.key = image.get('key')