diff --git a/Library/Homebrew/brew.sh b/Library/Homebrew/brew.sh
index d7d6f8b2f2..e2875794a7 100644
--- a/Library/Homebrew/brew.sh
+++ b/Library/Homebrew/brew.sh
@@ -51,9 +51,9 @@ HOMEBREW_CACHE="${HOMEBREW_CACHE:-${HOMEBREW_DEFAULT_CACHE}}"
 HOMEBREW_LOGS="${HOMEBREW_LOGS:-${HOMEBREW_DEFAULT_LOGS}}"
 HOMEBREW_TEMP="${HOMEBREW_TEMP:-${HOMEBREW_DEFAULT_TEMP}}"
 
-# These referenced variables are set by bin/brew
 # Don't need to handle a default case.
-# shellcheck disable=SC2154,SC2249
+# HOMEBREW_LIBRARY set by bin/brew
+# shellcheck disable=SC2249,SC2154
 case "$*" in
   --cellar)            echo "${HOMEBREW_CELLAR}"; exit 0 ;;
   --repository|--repo) echo "${HOMEBREW_REPOSITORY}"; exit 0 ;;
@@ -315,6 +315,8 @@ then
 fi
 
 HOMEBREW_CORE_REPOSITORY="${HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-core"
+# Used in --version.sh
+# shellcheck disable=SC2034
 HOMEBREW_CASK_REPOSITORY="${HOMEBREW_LIBRARY}/Taps/homebrew/homebrew-cask"
 
 case "$*" in
diff --git a/Library/Homebrew/cmd/formulae.sh b/Library/Homebrew/cmd/formulae.sh
index eee27c9629..ccf04ea076 100644
--- a/Library/Homebrew/cmd/formulae.sh
+++ b/Library/Homebrew/cmd/formulae.sh
@@ -3,7 +3,9 @@
 #:  List all locally installable formulae including short names.
 #:
 
-source "$HOMEBREW_LIBRARY/Homebrew/items.sh"
+# HOMEBREW_LIBRARY is set by bin/brew
+# shellcheck disable=SC2154
+source "${HOMEBREW_LIBRARY}/Homebrew/items.sh"
 
 homebrew-formulae() {
   homebrew-items 'Casks' 's|/Formula/|/|' '^homebrew/core'
diff --git a/Library/Homebrew/cmd/update.sh b/Library/Homebrew/cmd/update.sh
index 6d1e74f1ed..17f9c7903f 100644
--- a/Library/Homebrew/cmd/update.sh
+++ b/Library/Homebrew/cmd/update.sh
@@ -444,6 +444,8 @@ EOS
     QUIET_ARGS=()
   fi
 
+  # HOMEBREW_CURLRC isn't misspelt here
+  # shellcheck disable=SC2153
   if [[ -z "${HOMEBREW_CURLRC}" ]]
   then
     CURL_DISABLE_CURLRC_ARGS=(-q)
diff --git a/Library/Homebrew/cmd/vendor-install.sh b/Library/Homebrew/cmd/vendor-install.sh
index be4293183f..6c5d4878ab 100644
--- a/Library/Homebrew/cmd/vendor-install.sh
+++ b/Library/Homebrew/cmd/vendor-install.sh
@@ -82,6 +82,8 @@ fetch() {
   curl_args=()
 
   # do not load .curlrc unless requested (must be the first argument)
+  # HOMEBREW_CURLRC isn't misspelt here
+  # shellcheck disable=SC2153
   if [[ -z "${HOMEBREW_CURLRC}" ]]
   then
     curl_args[${#curl_args[*]}]="-q"
diff --git a/Library/Homebrew/completions/bash.erb b/Library/Homebrew/completions/bash.erb
index dfe77a08a9..71a72e6624 100644
--- a/Library/Homebrew/completions/bash.erb
+++ b/Library/Homebrew/completions/bash.erb
@@ -138,32 +138,32 @@ _brew() {
   local i=1 cmd
 
   # find the subcommand
-  while [[ "$i" -lt "$COMP_CWORD" ]]
+  while [[ "${i}" -lt "${COMP_CWORD}" ]]
   do
     local s="${COMP_WORDS[i]}"
-    case "$s" in
+    case "${s}" in
       --*)
-        cmd="$s"
+        cmd="${s}"
         break
         ;;
       -*)
         ;;
       *)
-        cmd="$s"
+        cmd="${s}"
         break
         ;;
     esac
     (( i++ ))
   done
 
-  if [[ "$i" -eq "$COMP_CWORD" ]]
+  if [[ "${i}" -eq "${COMP_CWORD}" ]]
   then
     __brew_complete_commands
     return
   fi
 
   # subcommands have their own completion functions
-  case "$cmd" in
+  case "${cmd}" in
     <%= function_mappings.join("\n    ").concat("\n") %>
     *) ;;
   esac
diff --git a/completions/bash/brew b/completions/bash/brew
index 85828ae500..68f056f099 100644
--- a/completions/bash/brew
+++ b/completions/bash/brew
@@ -2389,32 +2389,32 @@ _brew() {
   local i=1 cmd
 
   # find the subcommand
-  while [[ "$i" -lt "$COMP_CWORD" ]]
+  while [[ "${i}" -lt "${COMP_CWORD}" ]]
   do
     local s="${COMP_WORDS[i]}"
-    case "$s" in
+    case "${s}" in
       --*)
-        cmd="$s"
+        cmd="${s}"
         break
         ;;
       -*)
         ;;
       *)
-        cmd="$s"
+        cmd="${s}"
         break
         ;;
     esac
     (( i++ ))
   done
 
-  if [[ "$i" -eq "$COMP_CWORD" ]]
+  if [[ "${i}" -eq "${COMP_CWORD}" ]]
   then
     __brew_complete_commands
     return
   fi
 
   # subcommands have their own completion functions
-  case "$cmd" in
+  case "${cmd}" in
     --cache) _brew___cache ;;
     --caskroom) _brew___caskroom ;;
     --cellar) _brew___cellar ;;