Index: code/renderer/tr_local.h
===================================================================
--- code/renderer/tr_local.h	(revision 1386)
+++ code/renderer/tr_local.h	(working copy)
@@ -322,10 +322,15 @@
 
 struct shaderCommands_s;
 
-#define LIGHTMAP_2D			-4		// shader is for 2D rendering
-#define LIGHTMAP_BY_VERTEX	-3		// pre-lit triangle models
-#define LIGHTMAP_WHITEIMAGE	-2
-#define	LIGHTMAP_NONE		-1
+//
+// 080612 misantropia -- any change in
+// the LIGHTMAP_* defines here MUST be
+// reflected in R_FindShader() in tr_bsp.c
+//
+#define LIGHTMAP_2D         -4	// shader is for 2D rendering
+#define LIGHTMAP_BY_VERTEX  -3	// pre-lit triangle models
+#define LIGHTMAP_WHITEIMAGE -2
+#define LIGHTMAP_NONE       -1
 
 typedef enum {
 	CT_FRONT_SIDED,
Index: code/renderer/tr_shader.c
===================================================================
--- code/renderer/tr_shader.c	(revision 1386)
+++ code/renderer/tr_shader.c	(working copy)
@@ -2447,6 +2447,10 @@
 	// lightmaps
 	if ( lightmapIndex >= 0 && lightmapIndex >= tr.numLightmaps ) {
 		lightmapIndex = LIGHTMAP_BY_VERTEX;
+	} else if ( lightmapIndex < LIGHTMAP_2D ) {
+		// 080612 misantropia -- negative lightmap indexes cause stray pointers (think tr.lightmaps[lightmapIndex])
+		ri.Printf( PRINT_WARNING, "WARNING: shader '%s' has invalid lightmap index of %d\n", name, lightmapIndex  );
+		lightmapIndex = LIGHTMAP_BY_VERTEX;
 	}
 
 	COM_StripExtension(name, strippedName, sizeof(strippedName));