diff --git a/autoload/vimwiki/diary.vim b/autoload/vimwiki/diary.vim
index 66b92df..b47e6c9 100644
--- a/autoload/vimwiki/diary.vim
+++ b/autoload/vimwiki/diary.vim
@@ -523,7 +523,7 @@ endfunction
 function! vimwiki#diary#calendar_sign(day, month, year) abort
   " Callback function for Calendar.vim
   " Clause: no wiki no sign #290
-  if len(g:vimwiki_list) <= 0
+  if exists('g:vimwiki_list') && len(g:vimwiki_list) <= 0
     return
   endif
   let day = s:prefix_zero(a:day)
diff --git a/doc/vimwiki.txt b/doc/vimwiki.txt
index f5ff0ba..282e872 100644
--- a/doc/vimwiki.txt
+++ b/doc/vimwiki.txt
@@ -4002,6 +4002,7 @@ Contributors and their Github usernames in roughly chronological order:
     - Thomas Leyh (@leyhline)
     - nebulaeandstars (@nebulaeandstars)
     - dmitry kim (@jsn)
+    - Luke Atkinson (@LukeDAtkinson)
 
 ==============================================================================
 16. Changelog                                              *vimwiki-changelog*
@@ -4021,6 +4022,12 @@ This is somewhat experimental, and will probably be refined over time.
 
 2023.04.04~
 
+Fixed:~
+    * Issue #1336: vimwiki#diary#calendar_sign throws an error
+      when g:vimwiki_list is not set
+ 
+2023.04.04~
+
 New:~
     * Issue #1261: Feature: Support for <mark> in Markdown
       highlighting with yellow background and back foreground
diff --git a/plugin/vimwiki.vim b/plugin/vimwiki.vim
index 26f32c7..208540d 100644
--- a/plugin/vimwiki.vim
+++ b/plugin/vimwiki.vim
@@ -11,7 +11,7 @@ endif
 let g:loaded_vimwiki = 1
 
 " Set to version number for release:
-let g:vimwiki_version = '2023.04.04'
+let g:vimwiki_version = '2023.05.12'
 
 " Get the directory the script is installed in
 let s:plugin_dir = expand('<sfile>:p:h:h')
diff --git a/test/tag.vader b/test/tag.vader
index 1596412..5acd061 100644
--- a/test/tag.vader
+++ b/test/tag.vader
@@ -257,7 +257,7 @@ Expect (Correctly formatted tags file):
   !_TAG_PROGRAM_AUTHOR	Vimwiki
   !_TAG_PROGRAM_NAME	Vimwiki Tags
   !_TAG_PROGRAM_URL	https://github.com/vimwiki/vimwiki
-  !_TAG_PROGRAM_VERSION	2023.04.04
+  !_TAG_PROGRAM_VERSION	2023.05.12
   second-tag	Test-Tag.md	13;"	vimwiki:Test-Tag\tTest-Tag#second-tag\tTest-Tag#second-tag
   test-tag	Test-Tag.md	5;"	vimwiki:Test-Tag\tTest-Tag#a-header\tA header
   top-tag	Test-Tag.md	1;"	vimwiki:Test-Tag\tTest-Tag\tTest-Tag