diff --git a/datasette/publish/cloudrun.py b/datasette/publish/cloudrun.py
index 91408287..8271209a 100644
--- a/datasette/publish/cloudrun.py
+++ b/datasette/publish/cloudrun.py
@@ -160,6 +160,6 @@ def get_existing_services():
 
 
 def _validate_memory(ctx, param, value):
-    if re.match(r"^\d+(Gi|G|Mi|M)$", value) is None:
+    if value and re.match(r"^\d+(Gi|G|Mi|M)$", value) is None:
         raise click.BadParameter("--memory should be a number then Gi/G/Mi/M e.g 1Gi")
     return value
diff --git a/docs/datasette-publish-cloudrun-help.txt b/docs/datasette-publish-cloudrun-help.txt
index d1bc0a9a..f4ec6221 100644
--- a/docs/datasette-publish-cloudrun-help.txt
+++ b/docs/datasette-publish-cloudrun-help.txt
@@ -25,4 +25,5 @@ Options:
   --service TEXT                  Cloud Run service to deploy (or over-write)
   --spatialite                    Enable SpatialLite extension
   --show-files                    Output the generated Dockerfile and metadata.json
+  --memory TEXT                   Memory to allocate in Cloud Run, e.g. 1Gi
   --help                          Show this message and exit.