diff --git a/reactos/ntoskrnl/include/internal/ob.h b/reactos/ntoskrnl/include/internal/ob.h
index 5bfec12ef83..a78b5ad4579 100644
--- a/reactos/ntoskrnl/include/internal/ob.h
+++ b/reactos/ntoskrnl/include/internal/ob.h
@@ -268,16 +268,16 @@ ObKillProcess(
 NTSTATUS
 NTAPI
 ObpLookupObjectName(
-    IN HANDLE RootHandle,
-    IN PUNICODE_STRING ObjectName,
+    IN HANDLE RootHandle OPTIONAL,
+    IN OUT PUNICODE_STRING ObjectName,
     IN ULONG Attributes,
     IN POBJECT_TYPE ObjectType,
     IN KPROCESSOR_MODE AccessMode,
     IN OUT PVOID ParseContext,
-    IN PSECURITY_QUALITY_OF_SERVICE SecurityQos,
-    IN PVOID InsertObject,
-    IN PACCESS_STATE AccessState,
-    IN POBP_LOOKUP_CONTEXT LookupContext,
+    IN PSECURITY_QUALITY_OF_SERVICE SecurityQos OPTIONAL,
+    IN PVOID InsertObject OPTIONAL,
+    IN OUT PACCESS_STATE AccessState,
+    OUT POBP_LOOKUP_CONTEXT LookupContext,
     OUT PVOID *FoundObject
 );
 
diff --git a/reactos/ntoskrnl/ob/obname.c b/reactos/ntoskrnl/ob/obname.c
index b978a6bb0a9..849c79124b9 100644
--- a/reactos/ntoskrnl/ob/obname.c
+++ b/reactos/ntoskrnl/ob/obname.c
@@ -356,7 +356,7 @@ ObpDeleteNameCheck(IN PVOID Object)
 NTSTATUS
 NTAPI
 ObpLookupObjectName(IN HANDLE RootHandle OPTIONAL,
-                    IN PUNICODE_STRING ObjectName,
+                    IN OUT PUNICODE_STRING ObjectName,
                     IN ULONG Attributes,
                     IN POBJECT_TYPE ObjectType,
                     IN KPROCESSOR_MODE AccessMode,