diff --git a/src/hardware/r_opengl/r_opengl.c b/src/hardware/r_opengl/r_opengl.c
index 25bcf153bb5358620abcfe19e02d7006ef99ce7b..22b8675a0965c9274e9cd8b6c0d2aecaaa14419d 100644
--- a/src/hardware/r_opengl/r_opengl.c
+++ b/src/hardware/r_opengl/r_opengl.c
@@ -1520,7 +1520,7 @@ static void gld_BuildSky(int row_count, int col_count)
 	vertex_p = &vbo->data[0];
 	vbo->loopcount = 0;
 
-	for (yflip = 0; yflip < 2; yflip++)
+	for (yflip = 0; (UINT8)yflip < 2; yflip++)
 	{
 		vbo->loops[vbo->loopcount].mode = GL_TRIANGLE_FAN;
 		vbo->loops[vbo->loopcount].vertexindex = vertex_p - &vbo->data[0];