diff --git a/libs/app-error/src/lib.rs b/libs/app-error/src/lib.rs
index d74dd029..5ee18997 100644
--- a/libs/app-error/src/lib.rs
+++ b/libs/app-error/src/lib.rs
@@ -170,6 +170,9 @@ pub enum AppError {
     given_length: usize,
     max_length: usize,
   },
+
+  #[error("There is an invalid character in the publish namespace: {character}")]
+  CustomNamespaceInvalidCharacter { character: char },
 }
 
 impl AppError {
@@ -243,6 +246,9 @@ impl AppError {
       AppError::PublishNameAlreadyExists { .. } => ErrorCode::PublishNameAlreadyExists,
       AppError::PublishNameInvalidCharacter { .. } => ErrorCode::PublishNameInvalidCharacter,
       AppError::PublishNameTooLong { .. } => ErrorCode::PublishNameTooLong,
+      AppError::CustomNamespaceInvalidCharacter { .. } => {
+        ErrorCode::CustomNamespaceInvalidCharacter
+      },
     }
   }
 }
@@ -381,6 +387,7 @@ pub enum ErrorCode {
   PublishNameAlreadyExists = 1050,
   PublishNameInvalidCharacter = 1051,
   PublishNameTooLong = 1052,
+  CustomNamespaceInvalidCharacter = 1053,
 }
 
 impl ErrorCode {
diff --git a/src/biz/workspace/publish.rs b/src/biz/workspace/publish.rs
index 9ca6149f..06acb605 100644
--- a/src/biz/workspace/publish.rs
+++ b/src/biz/workspace/publish.rs
@@ -216,9 +216,7 @@ async fn check_workspace_namespace(new_namespace: &str) -> Result<(), AppError>
   // Only contain alphanumeric characters and hyphens
   for c in new_namespace.chars() {
     if !c.is_alphanumeric() && c != '-' {
-      return Err(AppError::InvalidRequest(
-        "Namespace must only contain alphanumeric characters and hyphens".to_string(),
-      ));
+      return Err(AppError::CustomNamespaceInvalidCharacter { character: c });
     }
   }
   Ok(())
diff --git a/tests/workspace/publish.rs b/tests/workspace/publish.rs
index 1f1eafa8..424cca3f 100644
--- a/tests/workspace/publish.rs
+++ b/tests/workspace/publish.rs
@@ -77,7 +77,12 @@ async fn test_set_publish_namespace_set() {
       .await
       .err()
       .unwrap();
-    assert_eq!(err.code, ErrorCode::InvalidRequest, "{:?}", err);
+    assert_eq!(
+      err.code,
+      ErrorCode::CustomNamespaceInvalidCharacter,
+      "{:?}",
+      err
+    );
   }
 }