diff --git a/core/libs/prx/libScePngDec/Export.cpp b/core/libs/prx/libScePngDec/Export.cpp
index cebcc9e3e..220f2aaee 100644
--- a/core/libs/prx/libScePngDec/Export.cpp
+++ b/core/libs/prx/libScePngDec/Export.cpp
@@ -55,6 +55,7 @@ static_assert(sizeof(Context) + HANDLE_ALIGNMENT - 1 <= MEMORY_SIZE);
 
 std::int32_t validateCreateParam(const PngDecCreateParam* param) {
     if (!param) return SCE_PNG_DEC_ERROR_INVALID_PARAM;
+    if (param->this_size != sizeof(PngDecCreateParam)) return SCE_PNG_DEC_ERROR_INVALID_SIZE;
     if (param->attribute != ATTRIBUTE_NONE && param->attribute != ATTRIBUTE_BIT_DEPTH_16) return SCE_PNG_DEC_ERROR_INVALID_PARAM;
     if (param->max_image_width == 0 || param->max_image_width - 1 > MAX_IMAGE_WIDTH) return SCE_PNG_DEC_ERROR_INVALID_SIZE;
     return 0;
diff --git a/core/libs/tests/GuestPngDec.cpp b/core/libs/tests/GuestPngDec.cpp
index 6bb53f9f6..f9536a50a 100644
--- a/core/libs/tests/GuestPngDec.cpp
+++ b/core/libs/tests/GuestPngDec.cpp
@@ -76,6 +76,8 @@ int main() {
     const std::int32_t memorySize = scePngDecQueryMemorySize(&param);
     Require(memorySize > 0);
     Require(scePngDecQueryMemorySize(nullptr) == invalidParam);
+    const PngDecCreateParam badSize{sizeof(PngDecCreateParam) - 1, 0, 1920};
+    Require(scePngDecQueryMemorySize(&badSize) == invalidSize);
     const PngDecCreateParam badAttribute{sizeof(PngDecCreateParam), 2, 1920};
     Require(scePngDecQueryMemorySize(&badAttribute) == invalidParam);
     const PngDecCreateParam zeroWidth{sizeof(PngDecCreateParam), 0, 0};
@@ -89,6 +91,7 @@ int main() {
     unsigned char* unaligned = memory.data() + 1;
     void* handle = nullptr;
     Require(scePngDecCreate(nullptr, unaligned, static_cast<std::uint32_t>(memorySize), &handle) == invalidParam);
+    Require(scePngDecCreate(&badSize, unaligned, static_cast<std::uint32_t>(memorySize), &handle) == invalidSize);
     Require(scePngDecCreate(&param, nullptr, static_cast<std::uint32_t>(memorySize), &handle) == invalidAddr);
     Require(scePngDecCreate(&param, unaligned, static_cast<std::uint32_t>(memorySize), nullptr) == invalidAddr);
     Require(scePngDecCreate(&param, unaligned, static_cast<std::uint32_t>(memorySize) - 1, &handle) == invalidWorkMemory);