diff --git a/Makefile b/Makefile
index 4c39949..bf3f73e 100644
--- a/Makefile
+++ b/Makefile
@@ -52,7 +52,6 @@ clean:
 run: build
 	DEBUG=routewatch ./bin/routewatch 2>&1 | tee log.txt
 
+# Rebuild the AS list built into RouteWatch from as.csv (needs the network).
 asupdate:
-	@echo "Updating AS info data..."
-	@go run cmd/asinfo-gen/main.go | gzip > pkg/asinfo/asdata.json.gz.tmp && \
-		mv pkg/asinfo/asdata.json.gz.tmp pkg/asinfo/asdata.json.gz
+	@script/asupdate
diff --git a/README.md b/README.md
index b459378..3ac623e 100644
--- a/README.md
+++ b/README.md
@@ -110,9 +110,10 @@ Every route answers `HEAD` as it answers `GET`, without the body.
       `handle` and `description`
 
     The search reads the AS list built into RouteWatch, not the database. The
-    list comes from [ipverse/asn-info](https://github.com/ipverse/asn-info). A
-    match can therefore be an AS that the database has no record of. A `q` that
-    is missing, empty or only spaces answers 400.
+    list comes from
+    [ipverse/as-metadata](https://github.com/ipverse/as-metadata). A match can
+    therefore be an AS that the database has no record of. A `q` that is
+    missing, empty or only spaces answers 400.
 
 A JSON answer is `{"status": "ok", "data": ...}`, or for an error
 `{"status": "error", "error": {"msg": ..., "code": ...}}`, and carries an
@@ -485,6 +486,11 @@ provide:
   or `go.sum`) and `go fmt` (writes), then `script/check`
 - `script/install-precommit` — install the git pre-commit hook that runs
   `script/precommit`
+- `script/asupdate` — rebuild the AS list built into RouteWatch,
+  `pkg/asinfo/asdata.json.gz`, from the `as.csv` file of
+  [ipverse/as-metadata](https://github.com/ipverse/as-metadata). It needs the
+  network. When the generator fails or finds no ASes, the old list stays and the
+  script exits non-zero.
 
 Tests and the linter run only in Docker, as the `test` and `lint` phases of the
 `Dockerfile`; the image cannot be built unless both pass. Every `docker build`
diff --git a/TODO.md b/TODO.md
index 9b0066a..c23f270 100644
--- a/TODO.md
+++ b/TODO.md
@@ -33,6 +33,11 @@ tested.
 
 # Completed Steps
 
+- 2026-10-27: `make asupdate` runs the new `script/asupdate`. It replaces the AS
+  list built into RouteWatch only when the generator succeeds and finds at least
+  one AS. A failed download used to replace the list with an empty file. The
+  generator reads `as.csv` from `ipverse/as-metadata`, the source's new name
+  (closes #173)
 - 2026-10-27: the WHOIS details of an AS at RIPE, APNIC or AFRINIC come only
   from its `aut-num` object and the organisation object it names. RIPE and APNIC
   start their answer with the `as-block` object of the AS's block. Its dates
diff --git a/cmd/asinfo-gen/main.go b/cmd/asinfo-gen/main.go
index 50040e4..1116588 100644
--- a/cmd/asinfo-gen/main.go
+++ b/cmd/asinfo-gen/main.go
@@ -15,7 +15,7 @@ import (
 	"strings"
 )
 
-const asCsvURL = "https://github.com/ipverse/asn-info/raw/refs/heads/master/as.csv"
+const asCsvURL = "https://github.com/ipverse/as-metadata/raw/refs/heads/master/as.csv"
 
 // The first columns of as.csv, the ones the generator reads. It reads past
 // the columns after them, such as the country code.
diff --git a/pkg/asinfo/doc.go b/pkg/asinfo/doc.go
index c26823c..ce8221f 100644
--- a/pkg/asinfo/doc.go
+++ b/pkg/asinfo/doc.go
@@ -2,7 +2,7 @@
 Package asinfo provides information about Autonomous Systems (AS).
 
 The package embeds a comprehensive database of AS numbers, handles, and descriptions
-sourced from https://github.com/ipverse/asn-info. The data is embedded at compile
+sourced from https://github.com/ipverse/as-metadata. The data is embedded at compile
 time and provides fast, offline lookups.
 
 Basic usage:
diff --git a/script/asupdate b/script/asupdate
new file mode 100755
index 0000000..f020c14
--- /dev/null
+++ b/script/asupdate
@@ -0,0 +1,43 @@
+#!/bin/sh
+# script/asupdate: rebuild the AS list built into RouteWatch from
+# as.csv with cmd/asinfo-gen. The new list replaces the old one only
+# when the generator succeeds and writes at least one AS. Otherwise
+# the old list stays as it was and the script exits non-zero.
+set -eu
+
+ROOT="$(cd "$(dirname "$0")/.." && pwd -P)"
+
+AS_DATA="pkg/asinfo/asdata.json.gz"
+# Next to AS_DATA, so the final mv is a rename on one file system.
+AS_DATA_TMP="$AS_DATA.tmp"
+
+main() {
+    cd "$ROOT"
+
+    json="$(mktemp)"
+    trap 'rm -f "$json" "$AS_DATA_TMP"' EXIT
+    # A signal exits through the EXIT trap too.
+    trap 'exit 1' HUP INT TERM
+
+    echo "Updating AS info data..."
+    if ! go run ./cmd/asinfo-gen >"$json"; then
+        echo "asupdate: the generator failed; $AS_DATA is unchanged" >&2
+        exit 1
+    fi
+
+    # The generator writes a list of ASes with "[" alone on the first
+    # line. An empty list is "[]", and no list at all is "null".
+    first_line=""
+    read -r first_line <"$json" || true
+    if [ "$first_line" != "[" ]; then
+        echo "asupdate: the generator wrote no ASes; $AS_DATA is unchanged" >&2
+        exit 1
+    fi
+
+    # -n leaves the time out of the file, so an unchanged list gives the
+    # same bytes.
+    gzip -n -c <"$json" >"$AS_DATA_TMP"
+    mv "$AS_DATA_TMP" "$AS_DATA"
+}
+
+main "$@"