diff --git a/include/functions b/include/functions
index 38cc46b3..f27211d0 100644
--- a/include/functions
+++ b/include/functions
@@ -2086,6 +2086,10 @@
         elif [ -n "${PKGINFOBINARY}" ]; then
             output=$(${PKGINFOBINARY} -q -e ${package} >/dev/null 2>&1)
             exit_code=$?  # 0=package installed, 1=package not installed
+        # Slackware also has RPM for some reason and that's why this test precedes the RPMBINARY test
+        elif [ "${OS_NAME}" = "Slackware Linux" -a -d "${ROOTDIR}/var/lib/pkgtools/packages" ]; then
+            output=$( ls ${ROOTDIR}/var/lib/pkgtools/packages/ 2> /dev/null | ${GREPBINARY} "^${package}-[^-]\+-[^-]\+-[^-]\+$" )
+            exit_code=$?
         elif [ -n "${RPMBINARY}" ]; then
             output=$(${RPMBINARY} --quiet -q ${package} > /dev/null 2>&1)
             exit_code=$?