diff --git a/bin/git-extras b/bin/git-extras
index 17d5692..c08257d 100755
--- a/bin/git-extras
+++ b/bin/git-extras
@@ -3,15 +3,15 @@
 VERSION="1.5.1"
 
 update() {
-  local binfile=$(which git-extras)
-  local binpath=${binfile%/*/*}
+  local bin=$(which git-extras)
+  local prefix=${bin%/*/*}
   local orig=$PWD
 
   cd /tmp \
     && rm -fr ./git-extras \
     && git clone --depth 1 https://github.com/visionmedia/git-extras.git \
     && cd git-extras \
-    && PREFIX=${binpath:=} make install \
+    && PREFIX="$prefix" make install \
     && cd "$orig" \
     && echo "... updated git-extras $VERSION -> $(git extras --version)"
 }