diff --git a/core/libs/prx/libkernel/File/include/FileFlags.hpp b/core/libs/prx/libkernel/File/include/FileFlags.hpp
index 2423ccdacf..374abfc4c5 100644
--- a/core/libs/prx/libkernel/File/include/FileFlags.hpp
+++ b/core/libs/prx/libkernel/File/include/FileFlags.hpp
@@ -19,4 +19,13 @@ constexpr std::int32_t SCE_KERNEL_O_NONBLOCK  = 0x00000004;
 constexpr std::int32_t SCE_KERNEL_O_DIRECT    = 0x00010000;
 constexpr std::int32_t SCE_KERNEL_O_DIRECTORY = 0x00020000;
 
+namespace File {
+
+constexpr bool InvalidOpenFlags(std::int32_t flags) {
+    constexpr std::int32_t createExclusiveDirectory = SCE_KERNEL_O_CREAT | SCE_KERNEL_O_EXCL | SCE_KERNEL_O_DIRECTORY;
+    return (flags & SCE_KERNEL_O_ACCMODE) == SCE_KERNEL_O_ACCMODE || (flags & createExclusiveDirectory) == createExclusiveDirectory;
+}
+
+}
+
 #endif
diff --git a/core/libs/prx/libkernel/File/src/Open.cpp b/core/libs/prx/libkernel/File/src/Open.cpp
index 8721a364f7..04beb97dd5 100644
--- a/core/libs/prx/libkernel/File/src/Open.cpp
+++ b/core/libs/prx/libkernel/File/src/Open.cpp
@@ -173,11 +173,6 @@ static int SceIoErrorFromErrno(int error) {
     return static_cast<int>(0x80020000u | static_cast<unsigned>(guest));
 }
 
-static bool InvalidOpenFlags(int flags) {
-    constexpr int createExclusiveDirectory = SCE_KERNEL_O_CREAT | SCE_KERNEL_O_EXCL | SCE_KERNEL_O_DIRECTORY;
-    return (flags & SCE_KERNEL_O_ACCMODE) == SCE_KERNEL_O_ACCMODE || (flags & createExclusiveDirectory) == createExclusiveDirectory;
-}
-
 static int OpenNative(const std::filesystem::path& native, int flags, std::uint16_t mode) {
 #ifdef _WIN32
     if ((flags & (SCE_KERNEL_O_DIRECTORY | SCE_KERNEL_O_CREAT)) == SCE_KERNEL_O_DIRECTORY) {
@@ -216,7 +211,7 @@ static int OpenNative(const std::filesystem::path& native, int flags, std::uint1
 extern "C" {
 
 int APS5_VABI sceKernelOpen(const char* path, int flags, std::uint16_t mode) {
-    if (InvalidOpenFlags(flags)) return SCE_KERNEL_ERROR_EINVAL;
+    if (File::InvalidOpenFlags(flags)) return SCE_KERNEL_ERROR_EINVAL;
     if (path != nullptr && *path == '\0') return SCE_KERNEL_ERROR_ENOENT;
     APS5_LOG_OUT("path=%s flags=0x%X nativeFlags=0x%X mode=0%o", path, flags, MapFlags(flags), mode);
     if (path != nullptr && File::IsRandomDevicePath(path)) {
@@ -233,7 +228,7 @@ int APS5_VABI sceKernelOpen(const char* path, int flags, std::uint16_t mode) {
 }
 
 int OpenInDirectory_nid_no_patch(int directory, const char* path, int flags, std::uint16_t mode) {
-    if (InvalidOpenFlags(flags)) return SCE_KERNEL_ERROR_EINVAL;
+    if (File::InvalidOpenFlags(flags)) return SCE_KERNEL_ERROR_EINVAL;
     int error = 0;
     const char* base = GetDirectoryDescriptorPath_nid_no_patch(directory, &error);
     if (base == nullptr) return SceErrorFromErrno(error);
diff --git a/core/libs/prx/libkernel/File/src/Stdio.cpp b/core/libs/prx/libkernel/File/src/Stdio.cpp
index 5ded00a7ba..5ecb117239 100644
--- a/core/libs/prx/libkernel/File/src/Stdio.cpp
+++ b/core/libs/prx/libkernel/File/src/Stdio.cpp
@@ -778,6 +778,7 @@ int APS5_VABI mkdir_nid_postfix(const char* path, uint16_t mode) {
 }
 
 int APS5_VABI open_nid_postfix(const char* path, int flags, int mode) {
+    if (File::InvalidOpenFlags(flags)) return PosixFailure(GUEST_EINVAL);
     if (const int error = PathError(path)) return PosixFailure(error);
     return PosixResult(sceKernelOpen(path, flags, static_cast<std::uint16_t>(mode)));
 }
diff --git a/core/libs/prx/libkernel_sys/Export.cpp b/core/libs/prx/libkernel_sys/Export.cpp
index 99809d6212..f2c7c888f7 100644
--- a/core/libs/prx/libkernel_sys/Export.cpp
+++ b/core/libs/prx/libkernel_sys/Export.cpp
@@ -424,6 +424,7 @@ int APS5_VABI openat_nid_postfix(int fd, const char* path, int flags, ...) {
         va_end(arguments);
 #endif
     }
+    if (File::InvalidOpenFlags(flags)) return static_cast<int>(Fail(GuestEinval));
     if (path == nullptr) return static_cast<int>(Fail(GuestEfault));
     if (*path == '\0') return static_cast<int>(Fail(GuestEnoent));
     if (fd == GuestAtFdcwd || *path == '/') return open_nid_postfix(path, flags, mode);
diff --git a/core/libs/tests/GuestFilesystem.cpp b/core/libs/tests/GuestFilesystem.cpp
index 796d213c71..6225846e87 100644
--- a/core/libs/tests/GuestFilesystem.cpp
+++ b/core/libs/tests/GuestFilesystem.cpp
@@ -858,6 +858,10 @@ int main() {
     Require(sceKernelOpen(invalidFlagsName.c_str(), 0x20a02, 0600) == static_cast<int>(0x80020016u));
     Require(open_nid_postfix(invalidFlagsName.c_str(), 0x20a00, 0600) == -1 && *__error_nid_postfix() == 22);
     Require(!std::filesystem::exists(invalidFlagsName));
+    Require(open_nid_postfix(nullptr, 3, 0) == -1 && *__error_nid_postfix() == 22);
+    Require(open_nid_postfix("", 0x20a00, 0600) == -1 && *__error_nid_postfix() == 22);
+    Require(_open_nid_postfix(nullptr, 0x403) == -1 && *__error_nid_postfix() == 22);
+    Require(_open_nid_postfix("", 3) == -1 && *__error_nid_postfix() == 22);
     Require(std::filesystem::file_size(present) == 5);
     Require(open_nid_postfix("", 0, 0) == -1 && *__error_nid_postfix() == 2);
     Require(_open_nid_postfix("", 0) == -1 && *__error_nid_postfix() == 2);
diff --git a/core/libs/tests/GuestKernelSys.cpp b/core/libs/tests/GuestKernelSys.cpp
index e557b1a1cc..a7e4532a36 100644
--- a/core/libs/tests/GuestKernelSys.cpp
+++ b/core/libs/tests/GuestKernelSys.cpp
@@ -325,6 +325,10 @@ int main() {
     Require(openat_nid_postfix(base, "missing.bin", SCE_KERNEL_O_RDONLY) == -1 && Error() == 2);
     Require(openat_nid_postfix(base, "file.txt", SCE_KERNEL_O_ACCMODE) == -1 && Error() == 22);
     Require(openat_nid_postfix(base, "absent.bin", SCE_KERNEL_O_WRONLY | SCE_KERNEL_O_CREAT | SCE_KERNEL_O_EXCL | SCE_KERNEL_O_DIRECTORY, 0644) == -1 && Error() == 22);
+    Require(openat_nid_postfix(base, nullptr, SCE_KERNEL_O_ACCMODE) == -1 && Error() == 22);
+    Require(openat_nid_postfix(base, "", SCE_KERNEL_O_ACCMODE) == -1 && Error() == 22);
+    Require(openat_nid_postfix(9999, "", SCE_KERNEL_O_WRONLY | SCE_KERNEL_O_CREAT | SCE_KERNEL_O_EXCL | SCE_KERNEL_O_DIRECTORY, 0644) == -1 && Error() == 22);
+    Require(openat_nid_postfix(-100, nullptr, SCE_KERNEL_O_ACCMODE) == -1 && Error() == 22);
     const auto guestFile = "/" + root.filename().string() + "/file.txt";
     const int absolute = openat_nid_postfix(-1, guestFile.c_str(), SCE_KERNEL_O_RDONLY);
     Require(absolute >= 0 && sceKernelClose(absolute) == 0);