diff --git a/mrustc/0001-dont-download-rustc.patch b/mrustc/0001-dont-download-rustc.patch
new file mode 100644
index 0000000..a595e5b
--- /dev/null
+++ b/mrustc/0001-dont-download-rustc.patch
@@ -0,0 +1,14 @@
+The $(RUSTC_SRC_DL) file already exists, but for some reason Make wants to rebuild
+this target when it has $(RUSTC_SRC_TARBALL) as a dependency.
+
+--- a/minicargo.mk
++++ b/minicargo.mk
+@@ -220,7 +220,7 @@ $(RUSTC_SRC_DL): rustc-$(RUSTC_VERSION)-src/extracted rustc-$(RUSTC_VERSION)-src
+ # - libstd, libpanic_unwind, libtest and libgetopts
+ # - libproc_macro (mrustc)
+ ifeq ($(USE_MERGED_BUILD),1)
+-$(RUSTCSRC)mrustc-stdlib/Cargo.toml: $(RUSTC_SRC_DL) minicargo.mk
++$(RUSTCSRC)mrustc-stdlib/Cargo.toml: minicargo.mk
+ 	@mkdir -p $(dir $@)
+ 	@echo "#![no_core]" > $(dir $@)/lib.rs
+ 	@echo "[package]" > $@
diff --git a/mrustc/package.az b/mrustc/package.az
new file mode 100644
index 0000000..7f18a7c
--- /dev/null
+++ b/mrustc/package.az
@@ -0,0 +1,64 @@
+package rustc-bootstrap-source {
+	description = "rustc source tree used by mrustc";
+	exclude = true;
+
+	version# = "1.90.0";
+	output = remoteTar {
+		url = "https://static.rust-lang.org/dist/rustc-"+version+"-src.tar.gz";
+		compress = gzip;
+		checksum = "kUjk5mOHRc7cTom0uJ5afFTkhFcXLYK8tJl_aqduffGSHc0TH_a-KKz6PI0nk_xK";
+	};
+	chmod = true;
+}
+
+package mrustc {
+	description = "alternative rust compiler (re-implementation)";
+	website = "https://github.com/thepowersgang/mrustc";
+	anitya = 391250;
+
+	version# = "0.12.0";
+	source = remoteGitHub {
+		suffix = "thepowersgang/mrustc";
+		tag = "v"+version;
+		checksum = "Db25OAKL_1yZIF6MlXOTHhrEJ-Pd-i-accVtt5rJollmpKm6B3bgS0xN7hoC1cVu";
+	};
+	patches = [ "0001-dont-download-rustc.patch" ];
+	extra = [ rustc-bootstrap-source ];
+
+	enterSource = true;
+	writable = true;
+	chmod = true;
+
+	minimal = true;
+	exec = make {
+		inPlace = true;
+		skipConfigure = true;
+		preMake = `
+sed -i 's/\$(shell git show --pretty=%H -s --no-show-signature)/unknown/' Makefile
+sed -i 's/\$(shell git show -s --pretty=%h --no-show-signature)/unknown/' Makefile
+sed -i 's/\$(shell git symbolic-ref -q --short HEAD || git describe --tags --exact-match)/v`+version+`/' Makefile
+sed -i 's/\$(shell git diff-index --quiet HEAD; echo $$?)/0/' Makefile
+sed -i 's/\$(shell env LC_TIME=C date -u +"%a, %e %b %Y %T +0000")/Thu,  1 Jan 1970 00:00:00 +0000/' Makefile
+
+export RUSTC_SOURCE='../extra/rustc-bootstrap-source'
+export RUSTC_VERSION="$(cut -d ' ' -f 1 "$RUSTC_SOURCE/version")"
+export MRUSTC_TARGET_VER="$(cut -d '.' -f 1,2 <<< "$RUSTC_VERSION")"
+export OUTDIR_SUF="-$RUSTC_VERSION"
+patch -d "$RUSTC_SOURCE" -p0 < "rustc-$RUSTC_VERSION-src.patch"
+touch "$RUSTC_SOURCE/dl-version"
+ln -s "$RUSTC_SOURCE" "rustc-$RUSTC_VERSION-src"
+`;
+		preCheck = `
+make -f minicargo.mk LIBS
+`;
+		check = [ "test" ];
+	};
+
+	inputs = [
+		bash,
+		patch,
+
+		// mrustc requires buggy gcc behaviour
+		gcc,
+	];
+}