diff --git a/Makefile b/Makefile
index f83ccb1..c743ecc 100644
--- a/Makefile
+++ b/Makefile
@@ -52,10 +52,10 @@ tippecanoe: geojson.o jsonpull/jsonpull.o tile.o pool.o mbtiles.o geometry.o pro
 tippecanoe-enumerate: enumerate.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CFLAGS) -o $@ $^ $(LDFLAGS) -lsqlite3
 
-tippecanoe-decode: decode.o projection.o mvt.o write_json.o
+tippecanoe-decode: decode.o projection.o mvt.o write_json.o text.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3
 
-tile-join: tile-join.o projection.o pool.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o
+tile-join: tile-join.o projection.o pool.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpull/jsonpull.o text.o write_json.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 unit: unit.o text.o
@@ -78,7 +78,7 @@ indent:
 TESTS = $(wildcard tests/*/out/*.json)
 SPACE = $(NULL) $(NULL)
 
-test: tippecanoe tippecanoe-decode $(addsuffix .check,$(TESTS)) raw-tiles-test parallel-test pbf-test join-test enumerate-test decode-test unit
+test: tippecanoe tippecanoe-decode $(addsuffix .check,$(TESTS)) raw-tiles-test parallel-test pbf-test join-test enumerate-test decode-test unit join-test-object
 	./unit
 
 # Work around Makefile and filename punctuation limits: _ for space, @ for :, % for /
@@ -199,6 +199,14 @@ join-test:
 	rm tests/join-population/tabblock_06001420.mbtiles tests/join-population/joined.mbtiles tests/join-population/joined-i.mbtiles tests/join-population/joined.mbtiles.json.check tests/join-population/joined-i.mbtiles.json.check tests/join-population/macarthur.mbtiles tests/join-population/merged.mbtiles tests/join-population/merged.mbtiles.json.check  tests/join-population/merged-folder.mbtiles tests/join-population/macarthur2.mbtiles tests/join-population/windows.mbtiles tests/join-population/windows-merged.mbtiles tests/join-population/windows-merged2.mbtiles tests/join-population/windows.mbtiles.json.check tests/join-population/just-macarthur.mbtiles tests/join-population/no-macarthur.mbtiles tests/join-population/just-macarthur.mbtiles.json.check tests/join-population/no-macarthur.mbtiles.json.check tests/join-population/merged-folder.mbtiles.json.check tests/join-population/windows-merged.mbtiles.json.check tests/join-population/windows-merged2.mbtiles.json.check tests/join-population/macarthur-and-macarthur2-merged.mbtiles tests/join-population/macarthur-and-macarthur2-merged2.mbtiles tests/join-population/macarthur-and-macarthur2-merged.mbtiles.json.check tests/join-population/macarthur-and-macarthur2-merged2.mbtiles.json.check
 	rm -rf tests/join-population/raw-merged-folder tests/join-population/tabblock_06001420-folder tests/join-population/macarthur-folder tests/join-population/macarthur2-folder tests/join-population/merged-mbtiles-to-folder tests/join-population/merged-folders-to-folder tests/join-population/windows-merged-folder tests/join-population/macarthur-and-macarthur2-folder
 
+join-test-object:
+	./tippecanoe -z0 -f -o tests/object/out/before.mbtiles tests/object/in.json
+	./tile-join -f -o tests/object/out/after.mbtiles tests/object/out/before.mbtiles
+	./tippecanoe-decode tests/object/out/before.mbtiles | grep -v '"bounds"' > tests/object/out/before.mbtiles.json
+	./tippecanoe-decode tests/object/out/after.mbtiles | grep -v '"bounds"' > tests/object/out/after.mbtiles.json
+	cmp tests/object/out/before.mbtiles.json tests/object/out/after.mbtiles.json
+	rm -f tests/object/out/before.mbtiles.json tests/object/out/after.mbtiles.json tests/object/out/before.mbtiles tests/object/out/after.mbtiles
+
 # Use this target to regenerate the standards that the tests are compared against
 # after making a change that legitimately changes their output
 
diff --git a/mbtiles.cpp b/mbtiles.cpp
index 8b1a83a..1f0588c 100644
--- a/mbtiles.cpp
+++ b/mbtiles.cpp
@@ -1,8 +1,3 @@
-// for vasprintf() on Linux
-#ifndef _GNU_SOURCE
-#define _GNU_SOURCE
-#endif
-
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
@@ -102,21 +97,6 @@ static void quote(std::string &buf, std::string const &s) {
 	}
 }
 
-void aprintf(std::string *buf, const char *format, ...) {
-	va_list ap;
-	char *tmp;
-
-	va_start(ap, format);
-	if (vasprintf(&tmp, format, ap) < 0) {
-		fprintf(stderr, "memory allocation failure\n");
-		exit(EXIT_FAILURE);
-	}
-	va_end(ap);
-
-	buf->append(tmp, strlen(tmp));
-	free(tmp);
-}
-
 bool type_and_string::operator<(const type_and_string &o) const {
 	if (string < o.string) {
 		return true;
diff --git a/mbtiles.hpp b/mbtiles.hpp
index 2e25262..7727c67 100644
--- a/mbtiles.hpp
+++ b/mbtiles.hpp
@@ -43,8 +43,6 @@ void mbtiles_write_metadata(sqlite3 *outdb, const char *outdir, const char *fnam
 
 void mbtiles_close(sqlite3 *outdb, const char *pgm);
 
-void aprintf(std::string *buf, const char *format, ...);
-
 std::map<std::string, layermap_entry> merge_layermaps(std::vector<std::map<std::string, layermap_entry> > const &maps);
 std::map<std::string, layermap_entry> merge_layermaps(std::vector<std::map<std::string, layermap_entry> > const &maps, bool trunc);
 
diff --git a/text.cpp b/text.cpp
index dc27d21..aee4713 100644
--- a/text.cpp
+++ b/text.cpp
@@ -1,5 +1,11 @@
+// for vasprintf() on Linux
+#ifndef _GNU_SOURCE
+#define _GNU_SOURCE
+#endif
+
 #include "text.hpp"
 #include <stdio.h>
+#include <stdlib.h>
 
 /**
  * Returns an empty string if `s` is valid utf8;
@@ -122,3 +128,18 @@ std::string truncate16(std::string const &s, size_t runes) {
 
 	return std::string(s, 0, lastgood - start);
 }
+
+void aprintf(std::string *buf, const char *format, ...) {
+	va_list ap;
+	char *tmp;
+
+	va_start(ap, format);
+	if (vasprintf(&tmp, format, ap) < 0) {
+		fprintf(stderr, "memory allocation failure\n");
+		exit(EXIT_FAILURE);
+	}
+	va_end(ap);
+
+	buf->append(tmp, strlen(tmp));
+	free(tmp);
+}
diff --git a/text.hpp b/text.hpp
index 65274a3..25a8a62 100644
--- a/text.hpp
+++ b/text.hpp
@@ -6,5 +6,6 @@
 std::string check_utf8(std::string text);
 const char *utf8_next(const char *s, long *c);
 std::string truncate16(std::string const &s, size_t runes);
+void aprintf(std::string *buf, const char *format, ...);
 
 #endif
diff --git a/tile-join.cpp b/tile-join.cpp
index 2f0414b..c04bb92 100644
--- a/tile-join.cpp
+++ b/tile-join.cpp
@@ -22,6 +22,8 @@
 #include "mbtiles.hpp"
 #include "geometry.hpp"
 #include "dirtiles.hpp"
+#include "write_json.hpp"
+#include "text.hpp"
 #include <fstream>
 #include <sstream>
 #include <algorithm>
@@ -171,6 +173,7 @@ void handle(std::string message, int z, unsigned x, unsigned y, std::map<std::st
 					type = mvt_double;
 				} else if (val.type == mvt_null || val.type == mvt_list || val.type == mvt_hash) {
 					type = mvt_hash;
+					stringify_val(value, feat, layer, val, feat.tags[t + 1]);
 				} else {
 					continue;
 				}
@@ -250,7 +253,12 @@ void handle(std::string message, int z, unsigned x, unsigned y, std::map<std::st
 					auto fa = attributes.find(k);
 
 					if (fa != attributes.end()) {
-						outlayer.tag(outfeature, k, fa->second.first);
+						if (fa->second.first.type == mvt_hash) {
+							copy_nested(layer, feat, k, fa->second.first, outlayer, outfeature);
+						} else {
+							outlayer.tag(outfeature, k, fa->second.first);
+						}
+
 						add_to_file_keys(file_keys->second.file_keys, k, fa->second.second);
 						attributes.erase(fa);
 					}
diff --git a/write_json.cpp b/write_json.cpp
index b652e3f..7dc46a9 100644
--- a/write_json.cpp
+++ b/write_json.cpp
@@ -7,6 +7,7 @@
 #include "geometry.hpp"
 #include "mvt.hpp"
 #include "write_json.hpp"
+#include "text.hpp"
 
 struct lonlat {
 	int op;
@@ -25,49 +26,74 @@ struct lonlat {
 };
 
 void print_val(FILE *fp, mvt_feature const &feature, mvt_layer const &layer, mvt_value const &val, size_t vo) {
+	std::string s;
+	stringify_val(s, feature, layer, val, vo);
+	fprintf(fp, "%s", s.c_str());
+}
+
+static void quote(std::string &buf, std::string const &s) {
+	buf.push_back('"');
+	for (size_t i = 0; i < s.size(); i++) {
+		unsigned char ch = s[i];
+
+		if (ch == '\\' || ch == '\"') {
+			buf.push_back('\\');
+			buf.push_back(ch);
+		} else if (ch < ' ') {
+			char tmp[7];
+			sprintf(tmp, "\\u%04x", ch);
+			buf.append(std::string(tmp));
+		} else {
+			buf.push_back(ch);
+		}
+	}
+	buf.push_back('"');
+}
+
+void stringify_val(std::string &out, mvt_feature const &feature, mvt_layer const &layer, mvt_value const &val, size_t vo) {
 	if (val.type == mvt_string) {
-		fprintq(fp, val.string_value.c_str());
+		quote(out, val.string_value);
 	} else if (val.type == mvt_int) {
-		fprintf(fp, "%lld", (long long) val.numeric_value.int_value);
+		out.append(std::to_string((long long) val.numeric_value.int_value));
 	} else if (val.type == mvt_double) {
 		double v = val.numeric_value.double_value;
 		if (v == (long long) v) {
-			fprintf(fp, "%lld", (long long) v);
+			out.append(std::to_string((long long) v));
 		} else {
-			fprintf(fp, "%g", v);
+			aprintf(&out, "%g", v);
 		}
 	} else if (val.type == mvt_float) {
 		double v = val.numeric_value.float_value;
 		if (v == (long long) v) {
-			fprintf(fp, "%lld", (long long) v);
+			out.append(std::to_string((long long) v));
 		} else {
-			fprintf(fp, "%g", v);
+			aprintf(&out, "%g", v);
 		}
 	} else if (val.type == mvt_sint) {
-		fprintf(fp, "%lld", (long long) val.numeric_value.sint_value);
+		out.append(std::to_string((long long) val.numeric_value.sint_value));
 	} else if (val.type == mvt_uint) {
-		fprintf(fp, "%lld", (long long) val.numeric_value.uint_value);
+		out.append(std::to_string((long long) val.numeric_value.uint_value));
 	} else if (val.type == mvt_bool) {
-		fprintf(fp, "%s", val.numeric_value.bool_value ? "true" : "false");
+		out.append(val.numeric_value.bool_value ? "true" : "false");
 	} else if (val.type == mvt_list) {
-		fprintf(fp, "[");
+		out.push_back('[');
 		for (size_t i = 0; i < val.list_value.size(); i++) {
 			if (i != 0) {
-				fprintf(fp, ",");
+				out.push_back(',');
 			}
 			if (val.list_value[i] >= vo || val.list_value[i] >= layer.values.size()) {
 				fprintf(stderr, "Invalid value reference in list (%lu from %lu within %lu)\n", val.list_value[i], vo,
 					layer.values.size());
 				exit(EXIT_FAILURE);
 			}
-			print_val(fp, feature, layer, layer.values[val.list_value[i]], val.list_value[i]);
+			stringify_val(out, feature, layer, layer.values[val.list_value[i]], val.list_value[i]);
 		}
-		fprintf(fp, "]");
+		out.push_back(']');
 	} else if (val.type == mvt_hash) {
-		fprintf(fp, "{");
+		out.push_back('{');
 		for (size_t i = 0; i + 1 < val.list_value.size(); i += 2) {
 			if (i != 0) {
-				fprintf(fp, ",");
+				out.push_back(',');
 			}
 			if (val.list_value[i] >= layer.keys.size()) {
 				fprintf(stderr, "Invalid key reference in hash (%lu from %lu within %lu)\n", val.list_value[i], vo, layer.keys.size());
@@ -78,13 +104,13 @@ void print_val(FILE *fp, mvt_feature const &feature, mvt_layer const &layer, mvt
 					vo, layer.values.size());
 				exit(EXIT_FAILURE);
 			}
-			fprintq(fp, layer.keys[val.list_value[i]].c_str());
-			fprintf(fp, ":");
-			print_val(fp, feature, layer, layer.values[val.list_value[i + 1]], val.list_value[i + 1]);
+			quote(out, layer.keys[val.list_value[i]]);
+			out.push_back(':');
+			stringify_val(out, feature, layer, layer.values[val.list_value[i + 1]], val.list_value[i + 1]);
 		}
-		fprintf(fp, "}");
+		out.push_back('}');
 	} else if (val.type == mvt_null) {
-		fprintf(fp, "null");
+		out.append("null");
 	}
 }
 
diff --git a/write_json.hpp b/write_json.hpp
index 38a611d..da4e4bb 100644
--- a/write_json.hpp
+++ b/write_json.hpp
@@ -1,2 +1,3 @@
 void layer_to_geojson(FILE *fp, mvt_layer const &layer, unsigned z, unsigned x, unsigned y, bool comma, bool name, bool zoom, unsigned long long index, long long sequence, long long extent, bool complain);
 void fprintq(FILE *f, const char *s);
+void stringify_val(std::string &out, mvt_feature const &feature, mvt_layer const &layer, mvt_value const &val, size_t vo);