diff --git a/Documentation/virt/kvm/api.rst b/Documentation/virt/kvm/api.rst
index 48f23bb80d7f5b290a0bc9476ccd910de3505f3c..622667cc87efc2f32261e49902aac98419cd1dc0 100644
--- a/Documentation/virt/kvm/api.rst
+++ b/Documentation/virt/kvm/api.rst
@@ -3763,7 +3763,7 @@ KVM_S390_MEMOP_F_INJECT_EXCEPTION is set.
 
 If the KVM_S390_MEMOP_F_SKEY_PROTECTION flag is set, storage key
 protection is also in effect and may cause exceptions if accesses are
-prohibited given the access key passed in "key".
+prohibited given the access key designated by "key"; the valid range is 0..15.
 KVM_S390_MEMOP_F_SKEY_PROTECTION is available if KVM_CAP_S390_MEM_OP_EXTENSION
 is > 0.