diff --git a/.github/workflows/stale.yml b/.github/workflows/stale.yml
index b14b1f62..c4ba4f38 100644
--- a/.github/workflows/stale.yml
+++ b/.github/workflows/stale.yml
@@ -22,14 +22,7 @@ jobs:
       with:
         repo-token: ${{ secrets.GITHUB_TOKEN }}
         stale-issue-label: 'stale'
-        exempt-issue-labels:
-          - 'category: Discussion'
-          - 'category: Feature Request'
-          - 'deferred'
-          - 'help needed: Open Research Problem'
-          - 'help needed: Request Input from Community'
-          - 'never stale'
-          - 'TODO: Documentation'
+        exempt-issue-labels: 'category: Discussion','category: Feature Request','deferred','help needed: Open Research Problem','help needed: Request Input from Community','never stale','TODO: Documentation'
         days-before-issue-stale: 30
         days-before-issue-close: 7
         stale-issue-message: 'This issue has been automatically marked as stale because it has not had recent activity. If there are no updates within 7 days it will be closed. You can add the "never stale" tag to prevent the issue from closing this issue.'
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 66a1244b..59bd8676 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -5,6 +5,10 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/),
 and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0.html).
 
+## [3.9.1] - 2024-06-28
+### Fixed
+- Fixed formatting error in `.github/workflows/stale.yml` that caused the Mark Stale Issues action not to run
+
 ## [3.9.0] - 2024-05-30
 ### Added
 - GitHub Action config file `.github/workflows/stale.yml`, which replaces StaleBot
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9ab6751f..d4d139d8 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -1,7 +1,7 @@
 # HEMCO/CMakeLists.txt
 
 cmake_minimum_required(VERSION 3.5)
-project(HEMCO VERSION 3.9.0 LANGUAGES Fortran)
+project(HEMCO VERSION 3.9.1 LANGUAGES Fortran)
 # Reminder: Make sure to also update version in src/Core/hco_error_mod.F90
 
 #-----------------------------------------------------------------------------
diff --git a/docs/source/conf.py b/docs/source/conf.py
index 3b0fe24f..02483613 100644
--- a/docs/source/conf.py
+++ b/docs/source/conf.py
@@ -23,7 +23,7 @@
 author = 'GEOS-Chem Support Team'
 
 # The full version, including alpha/beta/rc tags
-release = '3.9.0'
+release = '3.9.1'
 
 # -- General configuration ---------------------------------------------------
 
diff --git a/src/Core/hco_error_mod.F90 b/src/Core/hco_error_mod.F90
index 7139f382..197c45bc 100644
--- a/src/Core/hco_error_mod.F90
+++ b/src/Core/hco_error_mod.F90
@@ -105,7 +105,7 @@ MODULE HCO_Error_Mod
 #endif
 
   ! HEMCO version number.
-  CHARACTER(LEN=12), PARAMETER, PUBLIC :: HCO_VERSION = '3.9.0'
+  CHARACTER(LEN=12), PARAMETER, PUBLIC :: HCO_VERSION = '3.9.1'
 
   INTERFACE HCO_Error
      MODULE PROCEDURE HCO_ErrorNoErr