diff --git a/main.cpp b/main.cpp
index d803518..ac620e0 100644
--- a/main.cpp
+++ b/main.cpp
@@ -38,12 +38,12 @@ extern "C" {
 #include "jsonpull/jsonpull.h"
 }
 
+#include "mbtiles.hpp"
 #include "tile.hpp"
 #include "pool.hpp"
 #include "projection.hpp"
 #include "version.hpp"
 #include "memfile.hpp"
-#include "mbtiles.hpp"
 #include "main.hpp"
 #include "geojson.hpp"
 #include "geometry.hpp"
@@ -1661,7 +1661,7 @@ int read_input(std::vector<source> &sources, char *fname, const char *layername,
 	}
 
 	unsigned midx = 0, midy = 0;
-	int written = traverse_zooms(fd, size, meta, stringpool, &midx, &midy, layernames, maxzoom, minzoom, basezoom, outdb, droprate, buffer, fname, tmpdir, gamma, nlayers, full_detail, low_detail, min_detail, meta_off, pool_off, initial_x, initial_y, simplification);
+	int written = traverse_zooms(fd, size, meta, stringpool, &midx, &midy, layernames, maxzoom, minzoom, basezoom, outdb, droprate, buffer, fname, tmpdir, gamma, nlayers, full_detail, low_detail, min_detail, meta_off, pool_off, initial_x, initial_y, simplification, layermaps);
 
 	if (maxzoom != written) {
 		fprintf(stderr, "\n\n\n*** NOTE TILES ONLY COMPLETE THROUGH ZOOM %d ***\n\n\n", written);
diff --git a/serial.cpp b/serial.cpp
index fd98343..fa8cc38 100644
--- a/serial.cpp
+++ b/serial.cpp
@@ -5,8 +5,11 @@
 #include <string>
 #include <vector>
 #include <sqlite3.h>
+#include <set>
+#include <map>
 #include "protozero/varint.hpp"
 #include "geometry.hpp"
+#include "mbtiles.hpp"
 #include "tile.hpp"
 #include "serial.hpp"
 
diff --git a/tile.cpp b/tile.cpp
index 3293da8..0b38900 100644
--- a/tile.cpp
+++ b/tile.cpp
@@ -20,6 +20,7 @@
 #include <pthread.h>
 #include <errno.h>
 #include "mvt.hpp"
+#include "mbtiles.hpp"
 #include "geometry.hpp"
 #include "tile.hpp"
 #include "pool.hpp"
@@ -27,7 +28,6 @@
 #include "serial.hpp"
 #include "options.hpp"
 #include "main.hpp"
-#include "mbtiles.hpp"
 
 #define CMD_BITS 3
 
@@ -557,7 +557,7 @@ int manage_gap(unsigned long long index, unsigned long long *previndex, double s
 	return 0;
 }
 
-long long write_tile(FILE *geoms, long long *geompos_in, char *metabase, char *stringpool, int z, unsigned tx, unsigned ty, int detail, int min_detail, int basezoom, std::vector<std::string> *layernames, sqlite3 *outdb, double droprate, int buffer, const char *fname, FILE **geomfile, int minzoom, int maxzoom, double todo, volatile long long *along, long long alongminus, double gamma, int nlayers, int child_shards, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, volatile int *running, double simplification) {
+long long write_tile(FILE *geoms, long long *geompos_in, char *metabase, char *stringpool, int z, unsigned tx, unsigned ty, int detail, int min_detail, int basezoom, std::vector<std::string> *layernames, sqlite3 *outdb, double droprate, int buffer, const char *fname, FILE **geomfile, int minzoom, int maxzoom, double todo, volatile long long *along, long long alongminus, double gamma, int nlayers, int child_shards, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, volatile int *running, double simplification, std::vector<std::map<std::string, layermap_entry> > *layermaps) {
 	int line_detail;
 	double fraction = 1;
 
@@ -1155,6 +1155,7 @@ struct write_tile_args {
 	unsigned *initial_y;
 	volatile int *running;
 	int err;
+    std::vector<std::map<std::string, layermap_entry> > *layermaps;
 };
 
 void *run_thread(void *vargs) {
@@ -1195,7 +1196,7 @@ void *run_thread(void *vargs) {
 
 			// fprintf(stderr, "%d/%u/%u\n", z, x, y);
 
-			long long len = write_tile(geom, &geompos, arg->metabase, arg->stringpool, z, x, y, z == arg->maxzoom ? arg->full_detail : arg->low_detail, arg->min_detail, arg->basezoom, arg->layernames, arg->outdb, arg->droprate, arg->buffer, arg->fname, arg->geomfile, arg->minzoom, arg->maxzoom, arg->todo, arg->along, geompos, arg->gamma, arg->nlayers, arg->child_shards, arg->meta_off, arg->pool_off, arg->initial_x, arg->initial_y, arg->running, arg->simplification);
+			long long len = write_tile(geom, &geompos, arg->metabase, arg->stringpool, z, x, y, z == arg->maxzoom ? arg->full_detail : arg->low_detail, arg->min_detail, arg->basezoom, arg->layernames, arg->outdb, arg->droprate, arg->buffer, arg->fname, arg->geomfile, arg->minzoom, arg->maxzoom, arg->todo, arg->along, geompos, arg->gamma, arg->nlayers, arg->child_shards, arg->meta_off, arg->pool_off, arg->initial_x, arg->initial_y, arg->running, arg->simplification, arg->layermaps);
 
 			if (len < 0) {
 				int *err = &arg->err;
@@ -1246,7 +1247,7 @@ void *run_thread(void *vargs) {
 	return NULL;
 }
 
-int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpool, unsigned *midx, unsigned *midy, std::vector<std::string> &layernames, int maxzoom, int minzoom, int basezoom, sqlite3 *outdb, double droprate, int buffer, const char *fname, const char *tmpdir, double gamma, int nlayers, int full_detail, int low_detail, int min_detail, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification) {
+int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpool, unsigned *midx, unsigned *midy, std::vector<std::string> &layernames, int maxzoom, int minzoom, int basezoom, sqlite3 *outdb, double droprate, int buffer, const char *fname, const char *tmpdir, double gamma, int nlayers, int full_detail, int low_detail, int min_detail, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification, std::vector<std::map<std::string, layermap_entry> > &layermaps) {
 	int i;
 	for (i = 0; i <= maxzoom; i++) {
 		long long most = 0;
@@ -1382,6 +1383,7 @@ int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpo
 			args[thread].pool_off = pool_off;
 			args[thread].initial_x = initial_x;
 			args[thread].initial_y = initial_y;
+            args[thread].layermaps = &layermaps;
 
 			args[thread].tasks = dispatches[thread].tasks;
 			args[thread].running = &running;
diff --git a/tile.hpp b/tile.hpp
index 414ba3c..e6c25b5 100644
--- a/tile.hpp
+++ b/tile.hpp
@@ -1,5 +1,5 @@
 long long write_tile(char **geom, char *metabase, char *stringpool, unsigned *file_bbox, int z, unsigned x, unsigned y, int detail, int min_detail, int basezoom, char **layernames, sqlite3 *outdb, double droprate, int buffer, const char *fname, FILE **geomfile, int file_minzoom, int file_maxzoom, double todo, char *geomstart, long long along, double gamma, int nlayers);
 
-int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpool, unsigned *midx, unsigned *midy, std::vector<std::string> &layernames, int maxzoom, int minzoom, int basezoom, sqlite3 *outdb, double droprate, int buffer, const char *fname, const char *tmpdir, double gamma, int nlayers, int full_detail, int low_detail, int min_detail, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification);
+int traverse_zooms(int *geomfd, off_t *geom_size, char *metabase, char *stringpool, unsigned *midx, unsigned *midy, std::vector<std::string> &layernames, int maxzoom, int minzoom, int basezoom, sqlite3 *outdb, double droprate, int buffer, const char *fname, const char *tmpdir, double gamma, int nlayers, int full_detail, int low_detail, int min_detail, long long *meta_off, long long *pool_off, unsigned *initial_x, unsigned *initial_y, double simplification, std::vector<std::map<std::string, layermap_entry> > &layermap);
 
 int manage_gap(unsigned long long index, unsigned long long *previndex, double scale, double gamma, double *gap);