diff --git a/include/crypto/rng.h b/include/crypto/rng.h
index 8b4b844b..17bb3673 100644
--- a/include/crypto/rng.h
+++ b/include/crypto/rng.h
@@ -111,6 +111,8 @@ static inline struct rng_alg *crypto_rng_alg(struct crypto_rng *tfm)
 /**
  * crypto_free_rng() - zeroize and free RNG handle
  * @tfm: cipher handle to be freed
+ *
+ * If @tfm is a NULL or error pointer, this function does nothing.
  */
 static inline void crypto_free_rng(struct crypto_rng *tfm)
 {