diff --git a/Library/Homebrew/formula.rb b/Library/Homebrew/formula.rb
index a80ff7ac25..2e3ee7e9d2 100644
--- a/Library/Homebrew/formula.rb
+++ b/Library/Homebrew/formula.rb
@@ -2253,7 +2253,7 @@ class Formula
 
     os_versions = [*MacOSVersion::SYMBOLS.keys, :linux]
 
-    if path.exist? && self.class.on_system_blocks_exist?
+    if path.exist? && (self.class.on_system_blocks_exist? || @on_system_blocks_exist)
       formula_contents = path.read
       os_versions.product(OnSystem::ARCH_OPTIONS).each do |os, arch|
         bottle_tag = Utils::Bottles::Tag.new(system: os, arch: arch)