diff --git a/Library/Homebrew/cmd/formulae.sh b/Library/Homebrew/cmd/formulae.sh
index 649af45c9e..9812e9ce3c 100644
--- a/Library/Homebrew/cmd/formulae.sh
+++ b/Library/Homebrew/cmd/formulae.sh
@@ -8,5 +8,17 @@
 source "${HOMEBREW_LIBRARY}/Homebrew/items.sh"
 
 homebrew-formulae() {
-  homebrew-items '*\.rb' 'Casks' 's|/Formula/|/|' '^homebrew/core'
+  local formulae
+  formulae="$(homebrew-items '*\.rb' 'Casks' 's|/Formula/|/|' '^homebrew/core')"
+
+  # HOMEBREW_CACHE is set by brew.sh
+  # shellcheck disable=SC2154
+  if [[ -n "${HOMEBREW_INSTALL_FROM_API}" && -f "${HOMEBREW_CACHE}/api/formula.json" ]]
+  then
+    local api_formulae
+    api_formulae="$(ruby -e "require 'json'; JSON.parse(File.read('${HOMEBREW_CACHE}/api/formula.json')).each { |f| puts f['name'] }" 2>/dev/null)"
+    formulae="$(echo -e "${formulae}\n${api_formulae}" | sort -uf | grep .)"
+  fi
+
+  echo "${formulae}"
 }
diff --git a/Library/Homebrew/items.sh b/Library/Homebrew/items.sh
index 4a65589731..4c436fed39 100644
--- a/Library/Homebrew/items.sh
+++ b/Library/Homebrew/items.sh
@@ -17,6 +17,7 @@ homebrew-items() {
 
   # HOMEBREW_REPOSITORY is set by brew.sh
   # shellcheck disable=SC2154
+  [[ -d "${HOMEBREW_REPOSITORY}/Library/Taps" ]] || return
   items="$(
     find "${HOMEBREW_REPOSITORY}/Library/Taps" \
       -type d \( \