diff --git a/ref/gl/gl_local.h b/ref/gl/gl_local.h
index 8fadbc8d2..347b16912 100644
--- a/ref/gl/gl_local.h
+++ b/ref/gl/gl_local.h
@@ -812,6 +812,7 @@ extern convar_t r_shadows;
 extern convar_t r_ripple;
 extern convar_t r_ripple_updatetime;
 extern convar_t r_ripple_spawntime;
+extern convar_t r_large_lightmaps;
 
 //
 // engine shared convars
diff --git a/ref/gl/gl_opengl.c b/ref/gl/gl_opengl.c
index 826fe539f..e0316a20e 100644
--- a/ref/gl/gl_opengl.c
+++ b/ref/gl/gl_opengl.c
@@ -37,6 +37,7 @@ CVAR_DEFINE( r_vbo_overbrightmode, "gl_vbo_overbrightmode", "0", FCVAR_GLCONFIG,
 CVAR_DEFINE_AUTO( r_ripple, "0", FCVAR_GLCONFIG, "enable software-like water texture ripple simulation" );
 CVAR_DEFINE_AUTO( r_ripple_updatetime, "0.05", FCVAR_GLCONFIG, "how fast ripple simulation is" );
 CVAR_DEFINE_AUTO( r_ripple_spawntime, "0.1", FCVAR_GLCONFIG, "how fast new ripples spawn" );
+CVAR_DEFINE_AUTO( r_large_lightmaps, "0", FCVAR_GLCONFIG|FCVAR_LATCH, "enable larger lightmap atlas textures (might break custom renderer mods)" );
 
 DEFINE_ENGINE_SHARED_CVAR_LIST()
 
@@ -1147,6 +1148,7 @@ static void GL_InitCommands( void )
 	gEngfuncs.Cvar_RegisterVariable( &r_vbo_dlightmode );
 	gEngfuncs.Cvar_RegisterVariable( &r_vbo_overbrightmode );
 	gEngfuncs.Cvar_RegisterVariable( &r_vbo_detail );
+	gEngfuncs.Cvar_RegisterVariable( &r_large_lightmaps );
 
 	gEngfuncs.Cvar_RegisterVariable( &gl_extensions );
 	gEngfuncs.Cvar_RegisterVariable( &gl_texture_nearest );
diff --git a/ref/gl/gl_rsurf.c b/ref/gl/gl_rsurf.c
index 5e0239a93..30798e6d6 100644
--- a/ref/gl/gl_rsurf.c
+++ b/ref/gl/gl_rsurf.c
@@ -3858,7 +3858,7 @@ void GL_BuildLightmaps( void )
 	memset( &RI, 0, sizeof( RI ));
 
 	// update the lightmap blocksize
-	if( FBitSet( gp_host->features, ENGINE_LARGE_LIGHTMAPS ) || tr.world->version == QBSP2_VERSION )
+	if( FBitSet( gp_host->features, ENGINE_LARGE_LIGHTMAPS ) || tr.world->version == QBSP2_VERSION || r_large_lightmaps.value )
 		tr.block_size = BLOCK_SIZE_MAX;
 	else tr.block_size = BLOCK_SIZE_DEFAULT;