diff -pur a/src/gui/sdlmain.cpp b/src/gui/sdlmain.cpp
--- a/src/gui/sdlmain.cpp	2010-05-10 19:43:54.000000000 +0200
+++ b/src/gui/sdlmain.cpp	2017-09-01 15:37:29.000000000 +0200
@@ -1134,10 +1134,10 @@ static void GUI_StartUp(Section * sec) {
 #endif
 	const char * gl_ext = (const char *)glGetString (GL_EXTENSIONS);
 	if(gl_ext && *gl_ext){
-		sdl.opengl.packed_pixel=(strstr(gl_ext,"EXT_packed_pixels") > 0);
-		sdl.opengl.paletted_texture=(strstr(gl_ext,"EXT_paletted_texture") > 0);
+		sdl.opengl.packed_pixel=(strstr(gl_ext,"EXT_packed_pixels") != NULL);
+		sdl.opengl.paletted_texture=(strstr(gl_ext,"EXT_paletted_texture") != NULL);
 #if defined(NVIDIA_PixelDataRange)
-		sdl.opengl.pixel_data_range=(strstr(gl_ext,"GL_NV_pixel_data_range") >0 ) &&
+		sdl.opengl.pixel_data_range=(strstr(gl_ext,"GL_NV_pixel_data_range") != NULL) &&
 			glPixelDataRangeNV && db_glAllocateMemoryNV && db_glFreeMemoryNV;
 		sdl.opengl.pixel_data_range = 0;
 #endif