diff --git a/main/isl25/APKBUILD b/main/isl25/APKBUILD
new file mode 100644
index 0000000000000000000000000000000000000000..da1b133480b6730fe54fb78322d412c69d7323e1
--- /dev/null
+++ b/main/isl25/APKBUILD
@@ -0,0 +1,53 @@
+# Contributor: Timo Teräs <timo.teras@iki.fi>
+# Maintainer: Timo Teräs <timo.teras@iki.fi>
+
+# this package needs special care since it is a part of the toolchain.
+# we need to be able to have the old version installed in parallel with
+# a new with ABI breaking change. That is why we have the version
+# as a part of the pkgname.
+
+pkgname=isl25
+pkgver=0.25
+pkgrel=0
+pkgdesc="An Integer Set Library for the Polyhedral Model"
+url="http://isl.gforge.inria.fr/"
+arch="all"
+license="MIT"
+depends_dev="gmp-dev"
+makedepends_host="$depends_dev"
+makedepends="$makedepends_host"
+subpackages="isl-dev:_dev"
+source="https://libisl.sourceforge.io/isl-$pkgver.tar.bz2"
+
+builddir="$srcdir"/isl-$pkgver
+
+build() {
+	./configure \
+		--build=$CBUILD \
+		--host=$CHOST \
+		--prefix=/usr \
+		--mandir=/usr/share/man \
+		--infodir=/usr/share/info \
+		--localstatedir=/var \
+		--with-sysroot=${CBUILDROOT}
+	make
+}
+
+check() {
+	make check
+}
+
+package() {
+	make DESTDIR="$pkgdir" INSTALL="install -D" install
+}
+
+_dev() {
+	default_dev
+	mkdir -p "$subpkgdir"/usr/share/gdb/python/auto-load/usr/lib
+	mv "$pkgdir"/usr/lib/*-gdb.py \
+		"$subpkgdir"/usr/share/gdb/python/auto-load/usr/lib/
+}
+
+sha512sums="
+d309388d7dc1c861fddf74dbcc0f15b0166b166d0ed694473445ec47eb7d3dfab96412554016b3e06292f01967441546783ab329829dc4df4b9813716e2ef9ed  isl-0.25.tar.bz2
+"