diff --git a/scripts/circleci/set_up_github_keys.sh b/scripts/circleci/set_up_github_keys.sh
index 302c40eef0..4179f1e35b 100755
--- a/scripts/circleci/set_up_github_keys.sh
+++ b/scripts/circleci/set_up_github_keys.sh
@@ -2,9 +2,9 @@
 
 set -e
 
-if [ -n $GITHUB_TOKEN ]; then
+if [ -n "$GITHUB_TOKEN" ]; then
 
-  GH_PAGES_DIR=`pwd`/../react-gh-pages
+  GH_PAGES_DIR=$(pwd)/../react-gh-pages
   echo "machine github.com login reactjs-bot password $GITHUB_TOKEN" >~/.netrc
   git config --global user.name "Circle CI"
   git config --global user.email "circle@reactjs.org"
diff --git a/scripts/circleci/test_coverage.sh b/scripts/circleci/test_coverage.sh
index 91e12f5256..af5fa9b7b1 100755
--- a/scripts/circleci/test_coverage.sh
+++ b/scripts/circleci/test_coverage.sh
@@ -3,8 +3,8 @@
 set -e
 
 yarn test --coverage --maxWorkers=2
-if [ -z $CI_PULL_REQUEST ]; then
-  cat ./coverage/lcov.info | ./node_modules/.bin/coveralls
+if [ -z "$CI_PULL_REQUEST" ]; then
+  ./node_modules/.bin/coveralls < ./coverage/lcov.info
 fi
 
 # TODO: should we also track prod code coverage somehow?
diff --git a/scripts/circleci/track_stats.sh b/scripts/circleci/track_stats.sh
index a2f961cbe9..3f4238b9ae 100755
--- a/scripts/circleci/track_stats.sh
+++ b/scripts/circleci/track_stats.sh
@@ -2,7 +2,7 @@
 
 set -e
 
-ALL_FILES=`find packages -name '*.js' | grep -v umd/ | grep -v __tests__ | grep -v __mocks__`
-COUNT_ALL_FILES=`echo "$ALL_FILES" | wc -l`
-COUNT_WITH_FLOW=`grep '@flow' $ALL_FILES | perl -pe 's/:.+//' | wc -l`
+ALL_FILES=$(find packages -name '*.js' | grep -v umd/ | grep -v __tests__ | grep -v __mocks__)
+COUNT_ALL_FILES=$(echo "$ALL_FILES" | wc -l)
+COUNT_WITH_FLOW=$(grep '@flow' $ALL_FILES | perl -pe 's/:.+//' | wc -l)
 node scripts/facts-tracker/index.js "flow-files" "$COUNT_WITH_FLOW/$COUNT_ALL_FILES"
diff --git a/scripts/circleci/upload_build.sh b/scripts/circleci/upload_build.sh
index 26ae3e9bed..978acc296d 100755
--- a/scripts/circleci/upload_build.sh
+++ b/scripts/circleci/upload_build.sh
@@ -2,7 +2,7 @@
 
 set -e
 
-if [ -z $CI_PULL_REQUEST ] && [ -n "$BUILD_SERVER_ENDPOINT" ]; then
+if [ -z "$CI_PULL_REQUEST" ] && [ -n "$BUILD_SERVER_ENDPOINT" ]; then
   curl \
     -F "react.development=@build/dist/react.development.js" \
     -F "react.production.min=@build/dist/react.production.min.js" \
@@ -12,9 +12,9 @@ if [ -z $CI_PULL_REQUEST ] && [ -n "$BUILD_SERVER_ENDPOINT" ]; then
     -F "react-dom-server.browser.production.min=@build/dist/react-dom-server.browser.production.min.js" \
     -F "results.json=@build/../scripts/rollup/results.json" \
     -F "commit=$CIRCLE_SHA1" \
-    -F "date=`git log --format='%ct' -1`" \
+    -F "date=$(git log --format='%ct' -1)" \
     -F "pull_request=false" \
     -F "token=$BUILD_SERVER_TOKEN" \
     -F "branch=$CIRCLE_BRANCH" \
-    $BUILD_SERVER_ENDPOINT
+    "$BUILD_SERVER_ENDPOINT"
 fi