diff --git a/src/libromdata/tests/img/ImageDecoderTest.cpp b/src/libromdata/tests/img/ImageDecoderTest.cpp
index bd159ffae..46f392735 100644
--- a/src/libromdata/tests/img/ImageDecoderTest.cpp
+++ b/src/libromdata/tests/img/ImageDecoderTest.cpp
@@ -134,8 +134,8 @@ struct ImageDecoderTest_mode
 };
 
 // Maximum file size for images.
-static constexpr size_t MAX_DDS_IMAGE_FILESIZE = 12U*1024U*1024U;
-static constexpr size_t MAX_PNG_IMAGE_FILESIZE =  2U*1024U*1024U;
+static constexpr off64_t MAX_DDS_IMAGE_FILESIZE = 12U*1024U*1024U;
+static constexpr off64_t MAX_PNG_IMAGE_FILESIZE =  2U*1024U*1024U;
 
 class ImageDecoderTest : public ::testing::TestWithParam<ImageDecoderTest_mode>
 {
@@ -272,11 +272,9 @@ void ImageDecoderTest::SetUp(void)
 
 	/* FIXME: Per-type minimum sizes.
 	 * This fails on some very small SVR files.
-	ASSERT_GT(ddsSize, 4+sizeof(DDS_HEADER))
-		<< "DDS image is too small.";
+	ASSERT_GT(ddsSize, 4+sizeof(DDS_HEADER)) << "DDS image is too small.";
 	*/
-	ASSERT_LE(ddsSize, MAX_DDS_IMAGE_FILESIZE)
-		<< "DDS image is too big.";
+	ASSERT_LE(static_cast<off64_t>(ddsSize), MAX_DDS_IMAGE_FILESIZE) << "DDS image is too big.";
 
 	// Read the DDS image into memory.
 	m_dds_buf.resize(ddsSize);