diff --git a/Library/Homebrew/style.rb b/Library/Homebrew/style.rb
index d2e9dc2b63..98b31c9a03 100644
--- a/Library/Homebrew/style.rb
+++ b/Library/Homebrew/style.rb
@@ -164,14 +164,17 @@ module Homebrew
     end
 
     def run_shellcheck(files, output_type)
-      shellcheck   = Formula["shellcheck"].opt_bin/"shellcheck" if Formula["shellcheck"].latest_version_installed?
-      shellcheck ||= which("shellcheck")
-      shellcheck ||= which("shellcheck", ENV["HOMEBREW_PATH"])
-      shellcheck ||= begin
-        ohai "Installing `shellcheck` for shell style checks..."
-        safe_system HOMEBREW_BREW_FILE, "install", "shellcheck"
-        Formula["shellcheck"].opt_bin/"shellcheck"
+      # Always use the latest brewed shellcheck
+      unless Formula["shellcheck"].latest_version_installed?
+        if Formula["shellcheck"].any_version_installed?
+          ohai "Upgrading `shellcheck` for shell style checks..."
+          safe_system HOMEBREW_BREW_FILE, "upgrade", "shellcheck"
+        else
+          ohai "Installing `shellcheck` for shell style checks..."
+          safe_system HOMEBREW_BREW_FILE, "install", "shellcheck"
+        end
       end
+      shellcheck = Formula["shellcheck"].opt_bin/"shellcheck"
 
       if files.empty?
         files = [