diff --git a/system/mozilla-nss/mozilla-nss.SlackBuild b/system/mozilla-nss/mozilla-nss.SlackBuild
index e7110cea27..fc9c7f7f94 100644
--- a/system/mozilla-nss/mozilla-nss.SlackBuild
+++ b/system/mozilla-nss/mozilla-nss.SlackBuild
@@ -27,10 +27,17 @@ SRCNAM=nss
 VERSION=${VERSION:-3.12.4}
 NSPR=${NSPR:-4.8}
 
-ARCH=${ARCH:-i486}
 BUILD=${BUILD:-1}
 TAG=${TAG:-_SBo}
 
+if [ -z "$ARCH" ]; then
+  case "$( uname -m )" in
+    i?86) ARCH=i486 ;;
+    arm*) ARCH=arm ;;
+       *) ARCH=$( uname -m ) ;;
+  esac
+fi
+
 CWD=$(pwd)
 TMP=${TMP:-/tmp/SBo}
 PKG=$TMP/package-$PRGNAM