diff --git a/etc/tempest.conf.sample b/etc/tempest.conf.sample
index 28a4d1c..4bff20a 100644
--- a/etc/tempest.conf.sample
+++ b/etc/tempest.conf.sample
@@ -211,13 +211,14 @@
 # admin credentials are known. (boolean value)
 #allow_tenant_isolation=false
 
-# Valid primary image reference to be used in tests. (string
-# value)
-#image_ref={$IMAGE_ID}
+# Valid primary image reference to be used in tests. This is a
+# required option (string value)
+#image_ref=<None>
 
-# Valid secondary image reference to be used in tests. (string
-# value)
-#image_ref_alt={$IMAGE_ID_ALT}
+# Valid secondary image reference to be used in tests. This is
+# a required option, but if only one image is available
+# duplicate the value of image_ref above (string value)
+#image_ref_alt=<None>
 
 # Valid primary flavor to use in tests. (string value)
 #flavor_ref=1
diff --git a/tempest/config.py b/tempest/config.py
index f9be90d..db84607 100644
--- a/tempest/config.py
+++ b/tempest/config.py
@@ -137,11 +137,12 @@
                      "better parallel execution, but also requires that "
                      "OpenStack Identity API admin credentials are known."),
     cfg.StrOpt('image_ref',
-               default="{$IMAGE_ID}",
-               help="Valid primary image reference to be used in tests."),
+               help="Valid primary image reference to be used in tests. "
+                    "This is a required option"),
     cfg.StrOpt('image_ref_alt',
-               default="{$IMAGE_ID_ALT}",
-               help="Valid secondary image reference to be used in tests."),
+               help="Valid secondary image reference to be used in tests. "
+                    "This is a required option, but if only one image is "
+                    "available duplicate the value of image_ref above"),
     cfg.StrOpt('flavor_ref',
                default="1",
                help="Valid primary flavor to use in tests."),