diff --git a/doc/source/user/jobs.rst b/doc/source/user/jobs.rst
index f533f54..068da0b 100644
--- a/doc/source/user/jobs.rst
+++ b/doc/source/user/jobs.rst
@@ -278,14 +278,12 @@
 **zuul.oldrev**
   If the item was enqueued as the result of a tag being deleted, the
   previous git sha of the tag will be included here.  If the tag was
-  created, this will be set to the value
-  0000000000000000000000000000000000000000.
+  created, this variable will be undefined.
 
 **zuul.newrev**
   If the item was enqueued as the result of a tag being created, the
   new git sha of the tag will be included here.  If the tag was
-  deleted, this will be set to the value
-  0000000000000000000000000000000000000000.
+  deleted, this variable will be undefined.
 
 Ref Items
 +++++++++
@@ -298,14 +296,12 @@
 **zuul.oldrev**
   If the item was enqueued as the result of a ref being deleted, the
   previous git sha of the ref will be included here.  If the ref was
-  created, this will be set to the value
-  0000000000000000000000000000000000000000.
+  created, this variable will be undefined.
 
 **zuul.newrev**
   If the item was enqueued as the result of a ref being created, the
   new git sha of the ref will be included here.  If the ref was
-  deleted, this will be set to the value
-  0000000000000000000000000000000000000000.
+  deleted, this variable will be undefined.
 
 Working Directory
 +++++++++++++++++
diff --git a/zuul/executor/client.py b/zuul/executor/client.py
index cf70520..85ae68c 100644
--- a/zuul/executor/client.py
+++ b/zuul/executor/client.py
@@ -173,9 +173,11 @@
             zuul_params['change'] = str(item.change.number)
         if hasattr(item.change, 'patchset'):
             zuul_params['patchset'] = str(item.change.patchset)
-        if hasattr(item.change, 'oldrev') and item.change.oldrev:
+        if (hasattr(item.change, 'oldrev') and item.change.oldrev
+            and item.change.oldrev != '0' * 40):
             zuul_params['oldrev'] = item.change.oldrev
-        if hasattr(item.change, 'newrev') and item.change.newrev:
+        if (hasattr(item.change, 'newrev') and item.change.newrev
+            and item.change.newrev != '0' * 40):
             zuul_params['newrev'] = item.change.newrev
         zuul_params['items'] = []
         for i in all_items: