diff --git a/nu/tests.nu b/nu/tests.nu
index 0c6c8216e..2cadf4c5e 100644
--- a/nu/tests.nu
+++ b/nu/tests.nu
@@ -72,9 +72,13 @@ def run_test [test: record<name: string, execute: closure>]: nothing -> record<n
 }
 
 def format_error [error: string] {
-  $error
-    # Get the value for the text key in a partly non-json error message
+  # Get the value for the text key in a partly non-json error message
+  let parsed = $error
     | parse --regex ".+text: \"(.+)\""
+  if ($parsed | is-empty) {
+    return ''
+  }
+  $parsed
     | first
     | get capture0
     | str replace --all --regex "\\\\n" " "
@@ -101,7 +105,7 @@ def "test Nu version is correct" [] {
 
 def "test nu is added as a shell" [] {
   cat /etc/shells | print
-  let shell = cat /etc/shells
+  let shell = open /etc/shells
       | lines
       | where ($it | str contains "nu")
       | first
@@ -110,12 +114,12 @@ def "test nu is added as a shell" [] {
 }
 
 def 'test nu is not the only shell' [] {
-  let shells = cat /etc/shells
+  let shells = open /etc/shells
       | lines
       | where not ($it | str contains "nu")
       | length
 
-  assert greater $shells 1
+  assert greater $shells 0
 }
 
 def "test main plugins are installed" [] {
diff --git a/scripts/post-install.nu b/scripts/post-install.nu
index fb6805a58..3858f76c2 100755
--- a/scripts/post-install.nu
+++ b/scripts/post-install.nu
@@ -32,10 +32,18 @@ def 'setup-plugins' [] {
 
 # Add /usr/bin/nu to /etc/shells if it's not already there
 def 'add-shells' [] {
-  let shells = open /etc/shells
-  if not ($shells =~ $'/usr/bin/nu') {
-    echo $'/usr/bin/nu(char nl)' o>> /etc/shells
+  let content = open /etc/shells
+  const nu_bin = '/usr/bin/nu'
+  if ($content | str contains $nu_bin) {
+    return
   }
+  mut $new_line = $"($nu_bin)\n"
+  # Handle edge case when the content doesn't have ending newline,
+  # blindly appending the $new_line will end up writing to the same line.
+  if not ($content | str ends-with "\n") {
+    $new_line = "\n" ++ $new_line
+  }
+  echo $new_line o>> /etc/shells
 }
 
 def main [] {
diff --git a/scripts/pre-remove.nu b/scripts/pre-remove.nu
index 862469d56..24c32a7d5 100755
--- a/scripts/pre-remove.nu
+++ b/scripts/pre-remove.nu
@@ -5,11 +5,13 @@
 
 # Remove /usr/bin/nu from /etc/shells
 def 'remove-nu-from-shells' [] {
-  open /etc/shells
+  let new_content = open /etc/shells
     | lines
     | where $it !~ '/usr/bin/nu'
     | str join "\n"
-    | save -rf /etc/shells
+  # Keep a new line at the end of file to prevent other packages from making mistake
+  # when modifying this file.
+  $new_content ++ "\n" | save -rf /etc/shells
 }
 
 def main [] {