diff --git a/nix/packages/default.nix b/nix/packages/default.nix
index b7ad2b205..2228bfd11 100644
--- a/nix/packages/default.nix
+++ b/nix/packages/default.nix
@@ -5,6 +5,7 @@
     ./postgres-env.nix
     ./site-env.nix
     ./extension-catalog.nix
+    ./nix-dl.nix
   ];
   perSystem =
     {
diff --git a/nix/packages/extension-catalog.nix b/nix/packages/extension-catalog.nix
index d8d559121..7de8d0252 100644
--- a/nix/packages/extension-catalog.nix
+++ b/nix/packages/extension-catalog.nix
@@ -152,13 +152,14 @@
           name = "site-extensions-update";
           runtimeInputs = [
             self'.packages.site-extensions-resolve
+            self'.packages.nix-dl
             pkgs.nix
           ];
           text = ''
             manifest="''${1:?Usage: $0 path-to/pg-extensions.json}"
             profile="''${NIX_PROFILE:-/nix/var/nix/profiles/site-extensions}"
             readarray -t paths < <(site-extensions-resolve "$manifest")
-            nix-store -r --option stalled-download-timeout 120 "''${paths[@]}" >/dev/null
+            nix-dl "''${paths[@]}"
             nix-env --profile "$profile" --install "''${paths[@]}" --remove-all
           '';
         };
diff --git a/nix/packages/nix-dl.nix b/nix/packages/nix-dl.nix
new file mode 100644
index 000000000..c193112d3
--- /dev/null
+++ b/nix/packages/nix-dl.nix
@@ -0,0 +1,36 @@
+# Download nix store paths with timeout and retry.
+{
+  perSystem =
+    { pkgs, ... }:
+    {
+      packages.nix-dl = pkgs.writeShellApplication {
+        name = "nix-dl";
+        runtimeInputs = [
+          pkgs.coreutils
+          pkgs.nix
+        ];
+        text = ''
+          # nix-store -r can stall indefinitely: https://github.com/NixOS/nix/issues/8758
+          timeout_="''${NIX_DL_TIMEOUT:-120s}"
+          kill_grace="''${NIX_DL_KILL_GRACE:-10s}"
+          attempts="''${NIX_DL_ATTEMPTS:-3}"
+
+          for path in "$@"; do
+            ok="false"
+            for attempt in $(seq 1 "$attempts"); do
+              if timeout -k "$kill_grace" "$timeout_" nix-store -r "$path" >/dev/null; then
+                ok="true"
+                break
+              fi
+              if [ "$attempt" -lt "$attempts" ]; then
+                echo "WARNING: nix-store -r attempt $attempt/$attempts for $path failed or stalled (>=$timeout_ + up to $kill_grace kill grace); retrying" >&2
+              else
+                echo "ERROR: nix-store -r failed after $attempts attempts for $path" >&2
+              fi
+            done
+            [ "$ok" = "true" ] || exit 1
+          done
+        '';
+      };
+    };
+}