diff --git a/README.md b/README.md
index fc0f5ba..ee832f1 100644
--- a/README.md
+++ b/README.md
@@ -139,14 +139,14 @@ command. In `proot` mode, JuNest does no longer support the building of AUR pack
 first:
 
 ```sh
-pacman -Sy --ignore sudo base-devel
+pacman -Syu --ignore sudo base-devel
 :: sudo is in IgnorePkg/IgnoreGroup. Install anyway? [Y/n] n
 ...
 ...
 ```
 
 JuNest uses a modified version of `sudo`. That's why the original `sudo`
-package must be ignored in the previous command.
+package **must be ignored** in the previous command.
 
 Have fun!
 ---------
diff --git a/lib/core/namespace.sh b/lib/core/namespace.sh
index c80b80d..e9d3a53 100644
--- a/lib/core/namespace.sh
+++ b/lib/core/namespace.sh
@@ -27,7 +27,9 @@ function _is_user_namespace_enabled() {
         return $NOT_EXISTING_FILE
     fi
 
-    if ! zgrep_cmd -q "CONFIG_USER_NS=y" $config_file
+    # `-q` option in zgrep may cause a gzip: stdout: Broken pipe
+    # Use redirect to /dev/null instead
+    if ! zgrep_cmd "CONFIG_USER_NS=y" $config_file > /dev/null
     then
         return $NO_CONFIG_FOUND
     fi
@@ -37,7 +39,9 @@ function _is_user_namespace_enabled() {
         return 0
     fi
 
-    if ! zgrep_cmd -q "1" $PROC_USERNS_CLONE_FILE
+    # `-q` option in zgrep may cause a gzip: stdout: Broken pipe
+    # Use redirect to /dev/null instead
+    if ! zgrep_cmd "1" $PROC_USERNS_CLONE_FILE > /dev/null
     then
         return $UNPRIVILEGED_USERNS_DISABLED
     fi