diff --git a/CHANGELOG.md b/CHANGELOG.md
index ed03740..4add4ec 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,9 @@
+## [5.1.2](https://github.com/deshaw/jupyterlab-pyflyby/compare/v5.1.1...v5.1.2) (2024-02-28)
+
+### Fixed
+
+- Fix pyflyby messages check during nb cleanup
+
 ## [5.1.1](https://github.com/deshaw/jupyterlab-pyflyby/compare/v5.1.0...v5.1.1) (2024-02-20)
 
 ### Fixed
diff --git a/package.json b/package.json
index 2ff09d6..74af223 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@deshaw/jupyterlab-pyflyby",
-  "version": "5.1.1",
+  "version": "5.1.2",
   "description": "A labextension to integrate pyflyby with notebooks",
   "keywords": [
     "jupyter",
diff --git a/src/index.tsx b/src/index.tsx
index be6826f..5e57815 100644
--- a/src/index.tsx
+++ b/src/index.tsx
@@ -374,8 +374,8 @@ class PyflyByWidget extends Widget {
         // just have pyflyby messages
         if (
           line !== '' &&
-          line !== PYFLYBY_START_MSG &&
-          line !== PYFLYBY_END_MSG
+          line !== PYFLYBY_START_MSG.trim() &&
+          line !== PYFLYBY_END_MSG.trim()
         ) {
           shouldDelete = false;
         }