diff --git a/bin/brew b/bin/brew
index 654007e730..382c78f64e 100755
--- a/bin/brew
+++ b/bin/brew
@@ -3,18 +3,18 @@ chdir() {
   cd "$@" >/dev/null
 }
 
-BREW_FILE_DIRECTORY=$(chdir "${0%/*}" && pwd -P)
+BREW_FILE_DIRECTORY="$(chdir "${0%/*}" && pwd -P)"
 export HOMEBREW_BREW_FILE="$BREW_FILE_DIRECTORY/${0##*/}"
 
-BREW_SYMLINK=$(readlink "$0")
+BREW_SYMLINK="$(readlink "$0")"
 if [ -n "$BREW_SYMLINK" ]
 then
-  BREW_SYMLINK_DIRECTORY=$(dirname "$BREW_SYMLINK")
-  BREW_FILE_DIRECTORY=$(chdir "$BREW_FILE_DIRECTORY" &&
-                        chdir "$BREW_SYMLINK_DIRECTORY" && pwd -P)
+  BREW_SYMLINK_DIRECTORY="$(dirname "$BREW_SYMLINK")"
+  BREW_FILE_DIRECTORY="$(chdir "$BREW_FILE_DIRECTORY" &&
+                         chdir "$BREW_SYMLINK_DIRECTORY" && pwd -P)"
 fi
 
-BREW_LIBRARY_DIRECTORY=$(chdir "$BREW_FILE_DIRECTORY"/../Library && pwd -P)
+BREW_LIBRARY_DIRECTORY="$(chdir "$BREW_FILE_DIRECTORY"/../Library && pwd -P)"
 
 # Users may have these set, pointing the system Ruby
 # at non-system gem paths
@@ -28,7 +28,7 @@ fi
 
 if [ -z "$HOMEBREW_RUBY_PATH" ]
 then
-  BREW_SYSTEM=$(uname -s | tr "[:upper:]" "[:lower:]")
+  BREW_SYSTEM="$(uname -s | tr "[:upper:]" "[:lower:]")"
   if [ "$BREW_SYSTEM" = "darwin" ]
   then
     export HOMEBREW_RUBY_PATH="/System/Library/Frameworks/Ruby.framework/Versions/Current/usr/bin/ruby"