diff --git a/substrate/.gitlab-ci.yml b/substrate/.gitlab-ci.yml
index 15dd76a380..518f48be7c 100644
--- a/substrate/.gitlab-ci.yml
+++ b/substrate/.gitlab-ci.yml
@@ -52,6 +52,18 @@ check-runtime:
   script:
     - ./scripts/gitlab/check_runtime.sh
 
+
+check-line-width:
+  stage:                           test
+  image:                           parity/tools:latest
+  <<:                              *kubernetes-build
+  only:
+    - /^[0-9]+$/
+  script:
+    - ./scripts/gitlab/check_line_width.sh
+  allow_failure:                   false
+
+
 test-linux-stable:                 &test
   stage:                           test
   variables:
@@ -81,7 +93,7 @@ test-linux-stable:                 &test
 check-web-wasm:
   stage:                           test
   image:                           tomaka/cargo-web:latest
-  allow_failure: true
+  allow_failure:                   true
   only:
     - master
     - /^[0-9]+$/
diff --git a/substrate/scripts/gitlab/check_line_width.sh b/substrate/scripts/gitlab/check_line_width.sh
new file mode 100755
index 0000000000..ad78b24e11
--- /dev/null
+++ b/substrate/scripts/gitlab/check_line_width.sh
@@ -0,0 +1,49 @@
+#!/bin/sh
+#
+# check if line width of rust source files is not beyond x characters
+#
+
+
+BASE_BRANCH="origin/master"
+LINE_WIDTH="121"
+GOOD_LINE_WIDTH="101"
+
+
+git diff --name-only ${BASE_BRANCH}...${CI_COMMIT_SHA} \*.rs | ( while read file
+do
+  if git diff ${BASE_BRANCH}...${CI_COMMIT_SHA} ${file} | grep -q "^+.\{${LINE_WIDTH}\}"
+  then
+    if [ -z "${FAIL}" ]
+    then
+      echo "| warning!"
+      echo "| Lines should not be longer than 120 characters."
+      echo "| "
+      echo "| see more https://wiki.parity.io/Substrate-Style-Guide"
+      echo "|"
+      FAIL="true"
+    fi
+    echo "| file: ${file}"
+    git diff ${BASE_BRANCH}...${CI_COMMIT_SHA} ${file} \
+      | grep -n "^+.\{${LINE_WIDTH}\}"
+    echo "|"
+  else
+    if git diff ${BASE_BRANCH}...${CI_COMMIT_SHA} ${file} | grep -q "^+.\{${GOOD_LINE_WIDTH}\}"
+    then
+      if [ -z "${FAIL}" ]
+      then
+        echo "| warning!"
+        echo "| Lines should be longer than 100 characters only in exceptional circumstances!"
+        echo "| "
+        echo "| see more https://wiki.parity.io/Substrate-Style-Guide"
+        echo "|"
+      fi
+      echo "| file: ${file}"
+      git diff ${BASE_BRANCH}...${CI_COMMIT_SHA} ${file} \
+        | grep -n "^+.\{${LINE_WIDTH}\}"
+      echo "|"
+    fi
+  fi
+done
+
+test -z "${FAIL}"
+)