diff --git a/influxdb_iox_client/src/client/namespace.rs b/influxdb_iox_client/src/client/namespace.rs
index c91ebd50f1..f9bc513453 100644
--- a/influxdb_iox_client/src/client/namespace.rs
+++ b/influxdb_iox_client/src/client/namespace.rs
@@ -33,8 +33,11 @@ impl Client {
 
     /// Create a namespace
     ///
-    /// `retention_period_ns` is the the retention period in nanoseconds, measured from `now()`.
-    /// `None` represents infinite retention (i.e. never drop data).
+    /// `retention_period_ns` is the the retention period in nanoseconds,
+    /// measured from `now()`. `None` represents infinite retention (i.e. never
+    /// drop data), and 0 is also mapped to `None` on the server side.
+    ///
+    /// Negative retention periods are rejected, returning an error.
     pub async fn create_namespace(
         &mut self,
         namespace: &str,
@@ -53,8 +56,11 @@ impl Client {
 
     /// Update retention for a namespace
     ///
-    /// `retention_period_ns` is the the retention period in nanoseconds, measured from `now()`.
-    /// `None` represents infinite retention (i.e. never drop data).
+    /// `retention_period_ns` is the the retention period in nanoseconds,
+    /// measured from `now()`. `None` represents infinite retention (i.e. never
+    /// drop data), and 0 is also mapped to `None` on the server side.
+    ///
+    /// Negative retention periods are rejected, returning an error.
     pub async fn update_namespace_retention(
         &mut self,
         namespace: &str,