diff --git a/autoload/limelight.vim b/autoload/limelight.vim
index c52f10a..87c00ef 100644
--- a/autoload/limelight.vim
+++ b/autoload/limelight.vim
@@ -29,7 +29,7 @@ let g:loaded_limelight = 1
 let s:cpo_save = &cpo
 set cpo&vim
 
-let s:default_coeff = 0.5
+let s:default_coeff = str2float('0.5')
 let s:invalid_coefficient = 'Invalid coefficient. Expected: 0.0 ~ 1.0'
 
 function! s:unsupported()