diff --git a/tools/mozilla/build_firefox.sh b/tools/mozilla/build_firefox.sh
index e36adf3e1f..24feb021aa 100755
--- a/tools/mozilla/build_firefox.sh
+++ b/tools/mozilla/build_firefox.sh
@@ -66,9 +66,9 @@ LANGPACK_DIR="${BUILD_DIR}/xpi"
 FF_VERSION="4.0b7pre"
 
 # Include current dir in path (for buildxpi and others)
-CURDIR=`dirname $0`
-if [ x"$CURDIR" == x ] || [ x"$CURDIR" == x. ]; then
-    CURDIR=`pwd`
+CURDIR=$(dirname $0)
+if [ "$CURDIR" == "" -o  "$CURDIR" == '.' ]; then
+    CURDIR=$(pwd)
 fi
 PATH=${CURDIR}:${PATH}