diff --git a/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present.fail.sh b/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present.fail.sh
index 829ef5d6557..00ae6330142 100644
--- a/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present.fail.sh
+++ b/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present.fail.sh
@@ -5,14 +5,14 @@
 {{% if 'ubuntu' in product %}}
 for FILE in "/etc/pam.d/common-password"; do
     if ! grep -q "^[^#].*pam_unix\.so.*nullok" ${FILE}; then
-        sed -i 's/\([\s].*pam_unix\.so\)/\1 nullok/g' ${FILE}
+        sed -i 's/\(^[^#].*pam_unix\.so\)/\1 nullok/g' ${FILE}
     fi
 done
 {{% else %}}
 SYSTEM_AUTH_FILE="/etc/pam.d/system-auth"
 
 if ! $(grep -q "^[^#].*pam_unix\.so.*nullok" $SYSTEM_AUTH_FILE); then
-    sed -i --follow-symlinks 's/\([\s].*pam_unix\.so.*\)\s\(try_first_pass.*\)/\1nullok \2/' $SYSTEM_AUTH_FILE
+    sed -i --follow-symlinks 's/\(^[^#].*pam_unix\.so.*\)\s\(try_first_pass.*\)/\1nullok \2/' $SYSTEM_AUTH_FILE
 fi
 {{% endif %}}
 
diff --git a/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present_password_auth.fail.sh b/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present_password_auth.fail.sh
index effd5b7c066..88eb70d7020 100644
--- a/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present_password_auth.fail.sh
+++ b/linux_os/guide/system/accounts/accounts-restrictions/password_storage/no_empty_passwords/tests/nullok_present_password_auth.fail.sh
@@ -4,5 +4,5 @@
 PASSWORD_AUTH_FILE="/etc/pam.d/password-auth"
 
 if ! $(grep -q "^[^#].*pam_unix\.so.*nullok" $PASSWORD_AUTH_FILE); then
-    sed -i --follow-symlinks 's/\([\s].*pam_unix\.so.*\)\s\(try_first_pass.*\)/\1nullok \2/' $PASSWORD_AUTH_FILE
+    sed -i --follow-symlinks 's/\(^[^#].*pam_unix\.so.*\)\s\(try_first_pass.*\)/\1nullok \2/' $PASSWORD_AUTH_FILE
 fi