diff --git a/.github/workflows/tools.yml b/.github/workflows/tools.yml
index 95ffa9e9779f27..204d476df4b82f 100644
--- a/.github/workflows/tools.yml
+++ b/.github/workflows/tools.yml
@@ -38,6 +38,7 @@ on:
           - root-certificates
           - simdjson
           - sqlite
+          - test426-fixtures
           - undici
           - uvwasi
           - zlib
@@ -255,6 +256,14 @@ jobs:
               cat temp-output
               tail -n1 temp-output | grep "NEW_VERSION=" >> "$GITHUB_ENV" || true
               rm temp-output
+          - id: test426-fixtures
+            subsystem: test
+            label: test
+            run: |
+              bash tools/dep_updaters/update-test426-fixtures.sh > temp-output
+              cat temp-output
+              tail -n1 temp-output | grep "NEW_VERSION=" >> "$GITHUB_ENV" || true
+              rm temp-output
           - id: undici
             subsystem: deps
             label: dependencies
diff --git a/tools/dep_updaters/update-test426-fixtures.sh b/tools/dep_updaters/update-test426-fixtures.sh
new file mode 100755
index 00000000000000..730e7b67e35aa1
--- /dev/null
+++ b/tools/dep_updaters/update-test426-fixtures.sh
@@ -0,0 +1,29 @@
+#!/bin/sh
+
+set -ex
+
+BASE_DIR=$(cd "$(dirname "$0")/../.." && pwd)
+
+TARGET_DIR="$BASE_DIR/test/fixtures/test426"
+README="$BASE_DIR/test/test426/README.md"
+TARBALL_URL=$(curl -fsIo /dev/null -w '%header{Location}' https://github.com/tc39/source-map-tests/archive/HEAD.tar.gz)
+SHA=$(basename "$TARBALL_URL")
+
+CURRENT_SHA=$(sed -n 's#^.*https://github.com/tc39/source-map-tests/commit/\([0-9a-f]*\).*$#\1#p' "$README")
+
+if [ "$CURRENT_SHA" = "$SHA" ]; then
+  echo "Already up-to-date"
+  exit 0
+fi
+
+rm -rf "$TARGET_DIR"
+mkdir "$TARGET_DIR"
+curl -f "$TARBALL_URL" | tar -xz --strip-components 1 -C "$TARGET_DIR"
+
+TMP_FILE=$(mktemp)
+sed "s/$CURRENT_SHA/$SHA/" "$README" > "$TMP_FILE"
+mv "$TMP_FILE" "$README"
+
+# The last line of the script should always print the new version,
+# as we need to add it to $GITHUB_ENV variable.
+echo "NEW_VERSION=$SHA"