diff --git a/libraries/rxtx/rxtx.SlackBuild b/libraries/rxtx/rxtx.SlackBuild
index 01a23f167e..916390a4c5 100644
--- a/libraries/rxtx/rxtx.SlackBuild
+++ b/libraries/rxtx/rxtx.SlackBuild
@@ -6,12 +6,21 @@
 
 PRGNAM=rxtx
 VERSION=2.0_7pre2
-ARCH=${ARCH:-i486}
 BUILD=${BUILD:-2}
 TAG=${TAG:-_SBo}
 
 SRCVER=$(echo $VERSION | sed 's/_/-/')
 
+# Automatically determine the architecture we're building on:
+if [ -z "$ARCH" ]; then
+  case "$( uname -m )" in
+    i?86) ARCH=i486 ;;
+    arm*) ARCH=arm ;;
+    # Unless $ARCH is already set, use uname -m for all other archs:
+       *) ARCH=$( uname -m ) ;;
+  esac
+fi
+
 CWD=$(pwd)
 TMP=${TMP:-/tmp/SBo}
 PKG=$TMP/package-$PRGNAM
@@ -26,6 +35,9 @@ elif [ "$ARCH" = "i686" ]; then
 elif [ "$ARCH" = "x86_64" ]; then
   SLKCFLAGS="-O2 -fPIC"
   LIBDIRSUFFIX="64"
+else
+  SLKCFLAGS="-O2"
+  LIBDIRSUFFIX=""
 fi
 
 # Let's make sure that jdk is installed and the relevant environment variables