diff --git a/include/QF/model.h b/include/QF/model.h
index c33ec0006..fe1991ec6 100644
--- a/include/QF/model.h
+++ b/include/QF/model.h
@@ -482,4 +482,6 @@ extern char loadname[32];
 extern byte *mod_base;
 extern byte mod_novis[MAX_MAP_LEAFS / 8];
 
+extern int mod_lightmap_bytes;
+
 #endif	// _MODEL_H
diff --git a/libs/video/renderer/r_cvar.c b/libs/video/renderer/r_cvar.c
index 7bcdc510a..33ab20851 100644
--- a/libs/video/renderer/r_cvar.c
+++ b/libs/video/renderer/r_cvar.c
@@ -37,6 +37,7 @@ static const char rcsid[] =
 #endif
 
 #include "QF/cvar.h"
+#include "QF/model.h"
 
 #include "r_cvar.h"
 #include "r_dynamic.h"
@@ -146,6 +147,21 @@ r_particles_max_f (cvar_t *var)
 	R_MaxParticlesCheck (r_particles, var);
 }
 
+static void
+r_lightmap_components_f (cvar_t *var)
+{
+	switch (var->int_val) {
+		case 1:
+			mod_lightmap_bytes = 1;
+			break;
+		case 3:
+		case 4:
+		default:
+			mod_lightmap_bytes = 3;
+			break;
+	}
+}
+
 void
 R_Init_Cvars (void)
 {
@@ -278,7 +294,8 @@ R_Init_Cvars (void)
 							  "Set the number of lines displayed in the "
 							  "various graphs");
 	r_lightmap_components = Cvar_Get ("r_lightmap_components", "3", CVAR_ROM,
-									  NULL, "Lightmap texture components. 1 "
+									  r_lightmap_components_f,
+									  "Lightmap texture components. 1 "
 									  "is greyscale, 3 is RGB, 4 is RGBA.");
 	r_maxedges = Cvar_Get ("r_maxedges", "0", CVAR_NONE, NULL,
 						   "Sets the maximum number of edges");
diff --git a/nq/source/sv_model.c b/nq/source/sv_model.c
index 53d9c4472..f39e25c1f 100644
--- a/nq/source/sv_model.c
+++ b/nq/source/sv_model.c
@@ -35,7 +35,7 @@ static const char rcsid[] =
 #include "QF/cvar.h"
 #include "QF/model.h"
 
-const int   mod_lightmap_bytes = 1;
+int         mod_lightmap_bytes = 1;
 
 void Mod_LoadBrushModel (model_t *mod, void *buffer);
 
diff --git a/qw/source/sv_model.c b/qw/source/sv_model.c
index 53d9c4472..f39e25c1f 100644
--- a/qw/source/sv_model.c
+++ b/qw/source/sv_model.c
@@ -35,7 +35,7 @@ static const char rcsid[] =
 #include "QF/cvar.h"
 #include "QF/model.h"
 
-const int   mod_lightmap_bytes = 1;
+int         mod_lightmap_bytes = 1;
 
 void Mod_LoadBrushModel (model_t *mod, void *buffer);