diff --git a/Library/Homebrew/test.rb b/Library/Homebrew/test.rb
index 7a333b3606..1ba9396a79 100644
--- a/Library/Homebrew/test.rb
+++ b/Library/Homebrew/test.rb
@@ -16,7 +16,7 @@ require "cli/parser"
 require "dev-cmd/test"
 require "json/add/exception"
 
-TEST_TIMEOUT_SECONDS = 5 * 60
+DEFAULT_TEST_TIMEOUT_SECONDS = 5 * 60
 
 begin
   ENV.delete("HOMEBREW_FORBID_PACKAGES_FROM_PATHS")
@@ -49,7 +49,9 @@ begin
   if args.debug? # --debug is interactive
     run_test.call
   else
-    Timeout.timeout(TEST_TIMEOUT_SECONDS, &run_test)
+    # HOMEBREW_TEST_TIMEOUT_SECS is private API and subject to change.
+    timeout = ENV["HOMEBREW_TEST_TIMEOUT_SECS"]&.to_i || DEFAULT_TEST_TIMEOUT_SECONDS
+    Timeout.timeout(timeout, &run_test)
   end
 rescue Exception => e # rubocop:disable Lint/RescueException
   error_pipe.puts e.to_json