diff --git a/.circleci/config.yml b/.circleci/config.yml
index cc9b83a6..51bc7881 100644
--- a/.circleci/config.yml
+++ b/.circleci/config.yml
@@ -75,7 +75,7 @@ jobs:
             echo "########## clang-tidy-11 ##########"
             clang-tidy-11 src/* -- -I/usr/include -I/usr/include/ncursesw
             echo "########## shellcheck ##########"
-            find plugins/ -type f -not -name "*.md" -exec shellcheck -e SC1090,SC2230 {} +
+            find plugins/ -type f -not -name "*.md" -exec shellcheck {} +
 
   package-and-publish:
     machine: true
diff --git a/Makefile b/Makefile
index 721d0b67..3eaa28b7 100644
--- a/Makefile
+++ b/Makefile
@@ -261,6 +261,9 @@ musl:
 	./musl-static-ubuntu.sh 1
 	rm ./musl-static-ubuntu.sh
 
+shellcheck:
+	find ./plugins/ -type f -not -name "*.md" -exec shellcheck {} +
+
 dist:
 	mkdir -p nnn-$(VERSION)
 	$(CP) -r $(DISTFILES) nnn-$(VERSION)
diff --git a/misc/CONTRIBUTING.md b/misc/CONTRIBUTING.md
index 4fd61cd4..5b06c5f5 100644
--- a/misc/CONTRIBUTING.md
+++ b/misc/CONTRIBUTING.md
@@ -7,9 +7,10 @@ Before suggesting changes, please read a bit about [the design principles nnn fo
 
 `nnn` follows the Linux kernel coding style closely. The C source code uses TABs and the plugins use 4 spaces for indentation.
 
-Changes should not break the patch framework. Please run `make checkpatches` before raising a PR.
+- Code changes should not break the patch framework. Please run `make checkpatches` to ensure.
+- Run `make shellcheck` if adding/modifying plugins.
 
-CI runs `shellcheck` on plugins. Please watch out for any failures if you are modifying/adding a plugin.
+CI runs patch framework sanity test and `shellcheck`. Please watch out for any failures after raising the PR.
 
 ## Resources
 The [wiki](https://github.com/jarun/nnn/wiki/Developer-guides) has some resources for developers you might be interested in: building, debugging...
diff --git a/plugins/boom b/plugins/boom
index 77bb1b8c..aab466fa 100755
--- a/plugins/boom
+++ b/plugins/boom
@@ -9,7 +9,7 @@
 # Shell: POSIX compliant
 # Author: Arun Prakash Jana
 
-GUIPLAYER="${GUIPLAYER}"
+GUIPLAYER="${GUIPLAYER:-""}"
 NUMTRACKS="${NUMTRACKS:-100}"
 
 if [ -n "$GUIPLAYER" ]; then
diff --git a/plugins/cdpath b/plugins/cdpath
index 4ef0da23..663cb26a 100755
--- a/plugins/cdpath
+++ b/plugins/cdpath
@@ -16,6 +16,7 @@
 # Shell: POSIX compliant
 # Author: Yuri Kloubakov
 
+# shellcheck disable=SC1090,SC1091
 . "$(dirname "$0")"/.nnn-plugin-helper
 
 # Get a list of (symbolic links to) directories for every element of CDPATH
diff --git a/plugins/fzcd b/plugins/fzcd
index 28bd67e7..125092cb 100755
--- a/plugins/fzcd
+++ b/plugins/fzcd
@@ -22,10 +22,11 @@
 
 IFS="$(printf '\n\r')"
 
+# shellcheck disable=SC1090,SC1091
 . "$(dirname "$0")"/.nnn-plugin-helper
 
 CTX=+
-LIST="$LIST"
+LIST="${LIST:-""}"
 
 if ! type fzf >/dev/null 2>&1; then
     printf "fzf missing"
diff --git a/plugins/fzopen b/plugins/fzopen
index 57035b5c..17b05856 100755
--- a/plugins/fzopen
+++ b/plugins/fzopen
@@ -20,6 +20,7 @@
 NUKE="${XDG_CONFIG_HOME:-$HOME/.config}/nnn/plugins/nuke"
 USE_NUKE=0
 
+# shellcheck disable=SC1090,SC1091
 . "$(dirname "$0")"/.nnn-plugin-helper
 
 if type fzf >/dev/null 2>&1; then
diff --git a/plugins/gutenread b/plugins/gutenread
index ba41facd..036ff351 100755
--- a/plugins/gutenread
+++ b/plugins/gutenread
@@ -18,11 +18,11 @@
 # Shell: POSIX compliant
 # Author: Arun Prakash Jana
 
-EBOOK_ID="${EBOOK_ID}"
+EBOOK_ID="${EBOOK_ID:-""}"
 DIR="${XDG_CACHE_HOME:-$HOME/.cache}/nnn/gutenbooks/$EBOOK_ID"
 BROWSE_LINK="https://www.gutenberg.org/ebooks/search/?sort_order=downloads"
 BROWSER="${BROWSER:-w3m}"
-READER="${READER}"
+READER="${READER:-""}"
 
 if [ -n "$EBOOK_ID" ]; then
     if [ ! -e "$DIR" ]; then
diff --git a/plugins/imgur b/plugins/imgur
index 373de055..16d21bcd 100755
--- a/plugins/imgur
+++ b/plugins/imgur
@@ -112,6 +112,7 @@ check_update="true"
 
 settings_path="${HOME}/.config/imgur-screenshot/settings.conf"
 if [ -f "${settings_path}" ]; then
+  # shellcheck disable=SC1090
   source "${settings_path}"
 fi
 
@@ -204,6 +205,7 @@ function load_access_token() {
   token_expire_time=0
   # check for saved access_token and its expiration date
   if [ -f "${credentials_file}" ]; then
+    # shellcheck disable=SC1090
     source "${credentials_file}"
   fi
   current_time="$(date +%s)"
diff --git a/plugins/mimelist b/plugins/mimelist
index 586cc7cd..ccfe05a9 100755
--- a/plugins/mimelist
+++ b/plugins/mimelist
@@ -5,6 +5,7 @@
 # Shell: POSIX compliant
 # Author: Arun Prakash Jana
 
+# shellcheck disable=SC1090,SC1091
 . "$(dirname "$0")"/.nnn-plugin-helper
 
 printf "mime (e.g., video/audio/image): "