diff --git a/bin/mw b/bin/mw
index a415f0e..7eefed9 100755
--- a/bin/mw
+++ b/bin/mw
@@ -7,7 +7,7 @@ command -V gpg >/dev/null 2>&1 && GPG="gpg" || GPG="gpg2"
     }
 ! command -v mbsync >/dev/null && printf "\`mbsync\` must be installed to run mutt-wizard.\\n" && exit
 
-if [[ "$OSTYPE" == "darwin"* ]]; then
+if [ "$OSTYPE" = "darwin" ]; then
   prefix="/usr/local"
 else
   prefix="/usr"