diff --git a/pull-roms.sh b/pull-roms.sh
index b3cce65..ff3e65a 100755
--- a/pull-roms.sh
+++ b/pull-roms.sh
@@ -1,13 +1,14 @@
-TEMPDIR=$(pwd)/tmpdir
-FWDIR=$(pwd)/firmware
+TEMPDIR=${TEMPDIR:-$(pwd)/tmpdir}
+FWDIR=${FWDIR:-$(pwd)/firmware}
 
+mkdir -p $FWDIR
 
 echo Retrieving Bootloader from hpcalc.org for HP 49g+ and HP 50g...
 mkdir -p $TEMPDIR
 pushd $TEMPDIR
 wget https://www.hpcalc.org/hp49/pc/rom/hp-arm-models-bootloader.zip
 unzip -j hp-arm-models-bootloader.zip -d $TEMPDIR
-cp *.bin $FWDIR
+cp *.bin $FWDIR/
 popd
 rm -rf $TEMPDIR
 
@@ -17,7 +18,7 @@ mkdir -p $TEMPDIR
 pushd $TEMPDIR
 wget https://www.hpcalc.org/hp49/pc/rom/hp4950v215.zip
 unzip -j hp4950v215.zip -d $TEMPDIR
-cp *.bin $FWDIR
+cp *.bin $FWDIR/
 popd
 rm -rf $TEMPDIR
 
@@ -25,7 +26,6 @@ echo Retrieving latest Unofficial newRPL build...
 mkdir -p $TEMPDIR
 pushd $TEMPDIR
 wget https://hpgcc3.org/downloads/newrplfw.bin
-cp newrplfw.bin $FWDIR
+cp newrplfw.bin $FWDIR/
 popd
 rm -rf $TEMPDIR
-