diff --git a/zsh-history-substring-search.zsh b/zsh-history-substring-search.zsh
index e29c9b1..986b5f8 100644
--- a/zsh-history-substring-search.zsh
+++ b/zsh-history-substring-search.zsh
@@ -42,10 +42,12 @@
 # configuration variables
 #-----------------------------------------------------------------------------
 
-HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'
-HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'
-HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'
-HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE=''
+typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_FOUND='bg=magenta,fg=white,bold'
+typeset -g HISTORY_SUBSTRING_SEARCH_HIGHLIGHT_NOT_FOUND='bg=red,fg=white,bold'
+typeset -g HISTORY_SUBSTRING_SEARCH_GLOBBING_FLAGS='i'
+typeset -g HISTORY_SUBSTRING_SEARCH_ENSURE_UNIQUE=''
+typeset -g _history_substring_search_{refresh_display,query_highlight,result,query,match_index,raw_match_index}
+typeset -ga _history_substring_search{,_raw}_matches
 
 #-----------------------------------------------------------------------------
 # the main ZLE widgets