diff --git a/src/core/libraries/mouse/mouse.cpp b/src/core/libraries/mouse/mouse.cpp
index 988aa576f..fc447f284 100644
--- a/src/core/libraries/mouse/mouse.cpp
+++ b/src/core/libraries/mouse/mouse.cpp
@@ -81,15 +81,17 @@ int PS4_SYSV_ABI sceMouseOpen(Libraries::UserService::OrbisUserServiceUserId use
                               s32 index, OrbisMouseOpenParam* pParam) {
     LOG_WARNING(Lib_Mouse, "(DUMMY) called, uid: {}, type: {}, index: {}", userId, type, index);
     auto u = UserManagement.GetUserByID(userId);
-    if (!u || !pParam || (u8)pParam->flag > 1 || index < 0 || index > 1) {
+    if (!u || type != 0 || index < 0 || index > 1) {
         LOG_ERROR(Lib_Mouse, "invalid argument");
         return ORBIS_MOUSE_ERROR_INVALID_ARG;
     }
-    if (pParam->flag == MouseOpenBehaviour::Merged && index != 0) {
+    MouseOpenBehaviour mouse_mode = pParam ? pParam->flag : MouseOpenBehaviour::Normal;
+    bool merged_mode = True(mouse_mode & MouseOpenBehaviour::Merged);
+    if (merged_mode && index != 0) {
         LOG_ERROR(Lib_Mouse, "Only one mouse can be opened in merged mode!");
         return ORBIS_MOUSE_ERROR_ALREADY_OPENED;
     }
-    g_is_merged_mode = pParam->flag == MouseOpenBehaviour::Merged;
+    g_is_merged_mode = merged_mode;
     if (mouse_handles[index] != -1) {
         LOG_ERROR(Lib_Mouse, "already opened");
         return ORBIS_MOUSE_ERROR_ALREADY_OPENED;
diff --git a/src/core/libraries/mouse/mouse.h b/src/core/libraries/mouse/mouse.h
index b85cd6f59..d3ca483a6 100644
--- a/src/core/libraries/mouse/mouse.h
+++ b/src/core/libraries/mouse/mouse.h
@@ -3,6 +3,7 @@
 
 #pragma once
 
+#include "common/enum.h"
 #include "common/ring_buffer_queue.h"
 #include "core/libraries/system/userservice.h"
 
@@ -27,6 +28,7 @@ enum class MouseOpenBehaviour : u8 {
     Normal = 0,
     Merged = 1,
 };
+DECLARE_ENUM_FLAG_OPERATORS(MouseOpenBehaviour);
 
 struct OrbisMouseOpenParam {
     MouseOpenBehaviour flag;