diff --git a/kernel/capability.c b/kernel/capability.c
index c2316d3..c450375 100644
--- a/kernel/capability.c
+++ b/kernel/capability.c
@@ -169,8 +169,8 @@
 	kernel_cap_t pE, pI, pP;
 
 	ret = cap_validate_magic(header, &tocopy);
-	if (ret != 0)
-		return ret;
+	if ((dataptr == NULL) || (ret != 0))
+		return ((dataptr == NULL) && (ret == -EINVAL)) ? 0 : ret;
 
 	if (get_user(pid, &header->pid))
 		return -EFAULT;