diff --git a/changelog.d/8992.doc b/changelog.d/8992.doc
new file mode 100644
index 000000000..6a47bda26
--- /dev/null
+++ b/changelog.d/8992.doc
@@ -0,0 +1 @@
+Update the example value of `group_creation_prefix` in the sample configuration.
diff --git a/docs/sample_config.yaml b/docs/sample_config.yaml
index 0b4dd115f..dd981609a 100644
--- a/docs/sample_config.yaml
+++ b/docs/sample_config.yaml
@@ -2366,7 +2366,7 @@ spam_checker:
 # If enabled, non server admins can only create groups with local parts
 # starting with this prefix
 #
-#group_creation_prefix: "unofficial/"
+#group_creation_prefix: "unofficial_"
 
 
 
diff --git a/synapse/config/groups.py b/synapse/config/groups.py
index d6862d9a6..7b7860ea7 100644
--- a/synapse/config/groups.py
+++ b/synapse/config/groups.py
@@ -32,5 +32,5 @@ class GroupsConfig(Config):
         # If enabled, non server admins can only create groups with local parts
         # starting with this prefix
         #
-        #group_creation_prefix: "unofficial/"
+        #group_creation_prefix: "unofficial_"
         """