Diminishing is one of core features of use-package, normally
it would have to be required before using use-package.
This patch will load diminish when use-package loads.
index 1f3895f..a38ee48 100644
--- a/use-package-diminish.el
+++ b/use-package-diminish.el
@@ -33,6 +33,7 @@
 
 ;;; Code:
 
+(require 'diminish)
 (require 'use-package-core)
 
 (defun use-package-normalize-diminish (name label arg &optional recursed)