--- a/nsis-mode.el	Sun Mar 01 13:39:23 2015 +0200
+++ b/nsis-mode.el	Sun Mar 01 13:41:13 2015 +0200
@@ -79,7 +79,7 @@
   '(nsis-mode-modify-syntax-entry nsis-mode-set-comment-style)
   "Generic mode for nsis files.")
 
-(setq nsis-imenu-generic-expression
+(defvar nsis-imenu-generic-expression
       '(
         ("Defines"  "^!define[[:blank:]]+\\([[:word:]]+\\)" 1)
         ("Sections"  "^Section[[:blank:]]+\"?\\(-?[[:word:] ]+\\)\"?" 1)
@@ -93,9 +93,11 @@
 
 (add-hook 'nsis-mode-hook 'nsis-set-imenu-generic-expression)
 
+(eval-when-compile
+  (defvar which-func-modes))
+
 (eval-after-load 'which-func
-  '(add-to-list 'which-func-modes 'nsis-mode)
-  )
+  '(add-to-list 'which-func-modes 'nsis-mode))
 
 (provide 'nsis-mode)