diff --git a/src/osd/modules/font/font_sdl.cpp b/src/osd/modules/font/font_sdl.cpp
index c6f45635623..31ba1f13ba3 100644
--- a/src/osd/modules/font/font_sdl.cpp
+++ b/src/osd/modules/font/font_sdl.cpp
@@ -199,7 +199,7 @@ osd_font_sdl::TTF_Font_ptr osd_font_sdl::TTF_OpenFont_Magic(std::string const &n
 		unsigned char const ttf_magic[] = { 0x00, 0x01, 0x00, 0x00, 0x00 };
 		unsigned char const ttc1_magic[] = { 0x74, 0x74, 0x63, 0x66, 0x00, 0x01, 0x00, 0x00 };
 		unsigned char const ttc2_magic[] = { 0x74, 0x74, 0x63, 0x66, 0x00, 0x02, 0x00, 0x00 };
-		auto buffer_size = std::max({ sizeof(ttf_magic), sizeof(ttc1_magic), sizeof(ttc2_magic) });
+		constexpr auto buffer_size = std::max({ sizeof(ttf_magic), sizeof(ttc1_magic), sizeof(ttc2_magic) });
 		unsigned char buffer[buffer_size];
 		auto const bytes_read = file.read(buffer, buffer_size);
 		file.close();