diff --git a/Library/Homebrew/cask/audit.rb b/Library/Homebrew/cask/audit.rb
index 69479bd12f..ef237753ae 100644
--- a/Library/Homebrew/cask/audit.rb
+++ b/Library/Homebrew/cask/audit.rb
@@ -583,7 +583,7 @@ module Cask
       return if cask_min_os == min_os_string
 
       add_error "Upstream defined #{min_os_string.to_sym.inspect} as minimal OS version " \
-                "and the cask defined #{cask_min_os.to_sym.inspect}"
+                "and the cask defined #{cask_min_os ? cask_min_.to_sym.inspect : "no minimal OS version"}."
     end
 
     sig { void }