diff --git a/include/u-boot/rsa.h b/include/u-boot/rsa.h
index fd08a61..0e96c38 100644
--- a/include/u-boot/rsa.h
+++ b/include/u-boot/rsa.h
@@ -30,6 +30,8 @@
 	uint64_t exponent;	/* public exponent */
 };
 
+struct image_sign_info;
+
 #if IMAGE_ENABLE_SIGN
 /**
  * sign() - calculate and return signature for given input data