diff --git a/modules/nodejs/install.sh b/modules/nodejs/install.sh
index 0552227..86bf269 100755
--- a/modules/nodejs/install.sh
+++ b/modules/nodejs/install.sh
@@ -57,9 +57,11 @@ _ensure_npm_prefix() {
         # rewrite, not accept. (Reading the value to COMPARE is safe; we never re-emit
         # it — the rewrite below drops+appends rather than sed-substituting the path,
         # so a HOME with sed metacharacters can't break or inject the write.)
+        # `|| true`: an .npmrc with no prefix line (e.g. only an auth token) makes
+        # grep exit 1, which under pipefail + errexit would abort the module.
         local cur
         cur="$(grep -E '^[[:space:]]*prefix[[:space:]]*=' "$npmrc" | tail -1 \
-               | sed -E 's/^[[:space:]]*prefix[[:space:]]*=[[:space:]]*//; s/[[:space:]]*$//')"
+               | sed -E 's/^[[:space:]]*prefix[[:space:]]*=[[:space:]]*//; s/[[:space:]]*$//' || true)"
         [[ "$cur" == "$want" ]] && return 0
     fi
     local tmp; tmp="$(mktemp)"
diff --git a/test/integration/test_install.sh b/test/integration/test_install.sh
index cd55d92..66f401b 100755
--- a/test/integration/test_install.sh
+++ b/test/integration/test_install.sh
@@ -415,6 +415,9 @@ fi
 echo ""
 echo "--- Test: mise module + nodejs provider=mise (fixture overlay) ---"
 MISE_FIXTURE="${DOTFILES_DIR}/test/integration/fixtures/mise-overlay"
+# An existing ~/.npmrc with no prefix line (only a registry setting) must not
+# abort the nodejs module; the prefix is appended and the other line kept.
+printf '//registry.example.invalid/:always-auth=true\n' >"$HOME/.npmrc"
 MISE_OUT="$(env -u GITHUB_TOKEN -u MISE_GITHUB_TOKEN DOTFILES_CONTENT_DIR="$MISE_FIXTURE" \
     ./bin/dotfiles install --unattended mise nodejs extra-tools 2>&1)" || true
 assert_output_contains "mise + nodejs + overlay tool module install succeeded" "0 failed" "$MISE_OUT"
@@ -463,6 +466,11 @@ if [[ "$(zsh -c 'npm config get prefix' 2>/dev/null)" == "$HOME/.local" ]]; then
 else
     fail "npm global prefix stays ~/.local under the mise provider"
 fi
+if grep -qxF '//registry.example.invalid/:always-auth=true' "$HOME/.npmrc"; then
+    pass "prefix-less ~/.npmrc: existing settings preserved"
+else
+    fail "prefix-less ~/.npmrc: existing settings preserved"
+fi
 MISE_OUT2="$(env -u GITHUB_TOKEN -u MISE_GITHUB_TOKEN DOTFILES_CONTENT_DIR="$MISE_FIXTURE" \
     ./bin/dotfiles install --unattended mise nodejs extra-tools 2>&1)" || true
 assert_output_contains "mise re-install is a no-op" "0 succeeded, 0 failed" "$MISE_OUT2"