diff --git a/mbtiles.cpp b/mbtiles.cpp
index f56ea043..a9bed67c 100644
--- a/mbtiles.cpp
+++ b/mbtiles.cpp
@@ -261,7 +261,7 @@ void tilestats(std::map<std::string, layermap_entry> const &layermap1, size_t el
 		state.nospace = true;
 		state.json_write_string(geomtype);
 
-		size_t attrib_count = layer.second.file_keys.size();
+		size_t attrib_count = layer.second.tilestats.size();
 		if (attrib_count > max_tilestats_attributes) {
 			attrib_count = max_tilestats_attributes;
 		}
@@ -277,7 +277,7 @@ void tilestats(std::map<std::string, layermap_entry> const &layermap1, size_t el
 		state.json_write_array();
 
 		size_t attrs = 0;
-		for (auto attribute : layer.second.file_keys) {
+		for (auto attribute : layer.second.tilestats) {
 			if (attrs == elements) {
 				break;
 			}
@@ -745,7 +745,7 @@ metadata make_metadata(const char *fname, int minzoom, int maxzoom, double minla
 
 				bool first = true;
 				size_t attribute_count = 0;
-				for (auto j = fk->second.file_keys.begin(); j != fk->second.file_keys.end(); ++j) {
+				for (auto j = fk->second.tilestats.begin(); j != fk->second.tilestats.end(); ++j) {
 					if (first) {
 						first = false;
 					}
@@ -852,16 +852,16 @@ std::map<std::string, layermap_entry> merge_layermaps(std::vector<std::map<std::
 				exit(EXIT_IMPOSSIBLE);
 			}
 
-			for (auto fk = map->second.file_keys.begin(); fk != map->second.file_keys.end(); ++fk) {
+			for (auto fk = map->second.tilestats.begin(); fk != map->second.tilestats.end(); ++fk) {
 				std::string attribname = fk->first;
 				if (trunc) {
 					attribname = truncate16(attribname, 256);
 				}
 
-				auto fk2 = out_entry->second.file_keys.find(attribname);
+				auto fk2 = out_entry->second.tilestats.find(attribname);
 
-				if (fk2 == out_entry->second.file_keys.end()) {
-					out_entry->second.file_keys.insert(std::pair<std::string, tilestat>(attribname, fk->second));
+				if (fk2 == out_entry->second.tilestats.end()) {
+					out_entry->second.tilestats.insert(std::pair<std::string, tilestat>(attribname, fk->second));
 				} else {
 					for (auto val : fk->second.sample_values) {
 						auto pt = std::lower_bound(fk2->second.sample_values.begin(), fk2->second.sample_values.end(), val);
@@ -901,18 +901,18 @@ std::map<std::string, layermap_entry> merge_layermaps(std::vector<std::map<std::
 	return out;
 }
 
-void add_to_file_keys(std::map<std::string, tilestat> &file_keys, std::string const &attrib, serial_val const &val) {
+void add_to_tilestats(std::map<std::string, tilestat> &tilestats, std::string const &attrib, serial_val const &val) {
 	if (val.type == mvt_null) {
 		return;
 	}
 
-	auto fka = file_keys.find(attrib);
-	if (fka == file_keys.end()) {
-		file_keys.insert(std::pair<std::string, tilestat>(attrib, tilestat()));
-		fka = file_keys.find(attrib);
+	auto fka = tilestats.find(attrib);
+	if (fka == tilestats.end()) {
+		tilestats.insert(std::pair<std::string, tilestat>(attrib, tilestat()));
+		fka = tilestats.find(attrib);
 	}
 
-	if (fka == file_keys.end()) {
+	if (fka == tilestats.end()) {
 		fprintf(stderr, "Can't happen (tilestats)\n");
 		exit(EXIT_IMPOSSIBLE);
 	}
diff --git a/mbtiles.hpp b/mbtiles.hpp
index 52c19517..b1837668 100644
--- a/mbtiles.hpp
+++ b/mbtiles.hpp
@@ -18,7 +18,7 @@ struct tilestat {
 
 struct layermap_entry {
 	size_t id = 0;
-	std::map<std::string, tilestat> file_keys{};
+	std::map<std::string, tilestat> tilestats{};
 	int minzoom = 0;
 	int maxzoom = 0;
 	std::string description = "";
@@ -76,7 +76,7 @@ void mbtiles_close(sqlite3 *outdb, const char *pgm);
 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);
 
-void add_to_file_keys(std::map<std::string, tilestat> &file_keys, std::string const &layername, serial_val const &val);
+void add_to_tilestats(std::map<std::string, tilestat> &tilestats, std::string const &layername, serial_val const &val);
 
 unsigned long long fnv1a(std::string const &s);
 
diff --git a/plugin.cpp b/plugin.cpp
index 30ee0fdb..1ace7d96 100644
--- a/plugin.cpp
+++ b/plugin.cpp
@@ -278,7 +278,7 @@ std::vector<mvt_layer> parse_layers(int fd, int z, unsigned x, unsigned y, std::
 					attrib.type = tp;
 					attrib.s = s;
 
-					add_to_file_keys(fk->second.file_keys, std::string(properties->value.object.keys[i]->value.string.string), attrib);
+					add_to_tilestats(fk->second.tilestats, std::string(properties->value.object.keys[i]->value.string.string), attrib);
 				}
 			}
 
@@ -520,7 +520,7 @@ serial_feature parse_feature(json_pull *jp, int z, unsigned x, unsigned y, std::
 					attrib.type = v.type;
 
 					if (!postfilter) {
-						add_to_file_keys(fk->second.file_keys, std::string(properties->value.object.keys[i]->value.string.string), attrib);
+						add_to_tilestats(fk->second.tilestats, std::string(properties->value.object.keys[i]->value.string.string), attrib);
 					}
 				}
 			}
diff --git a/serial.cpp b/serial.cpp
index 7317a851..bcd7c540 100644
--- a/serial.cpp
+++ b/serial.cpp
@@ -828,7 +828,7 @@ int serialize_feature(struct serialization_state *sst, serial_feature &sf) {
 	if (!sst->filters) {
 		for (size_t i = 0; i < sf.full_keys.size(); i++) {
 			auto fk = sst->layermap->find(sf.layername);
-			add_to_file_keys(fk->second.file_keys, sf.full_keys[i], sf.full_values[i]);
+			add_to_tilestats(fk->second.tilestats, sf.full_keys[i], sf.full_values[i]);
 		}
 	}
 
diff --git a/tile-join.cpp b/tile-join.cpp
index 32ed5a52..7354a960 100644
--- a/tile-join.cpp
+++ b/tile-join.cpp
@@ -149,7 +149,7 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 			}
 		}
 
-		auto file_keys = layermap.find(layer.name);
+		auto tilestats = layermap.find(layer.name);
 
 		for (size_t f = 0; f < layer.features.size(); f++) {
 			mvt_feature feat = layer.features[f];
@@ -269,11 +269,11 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 			}
 
 			if (matched || !ifmatched) {
-				if (file_keys == layermap.end()) {
+				if (tilestats == layermap.end()) {
 					layermap.insert(std::pair<std::string, layermap_entry>(layer.name, layermap_entry(layermap.size())));
-					file_keys = layermap.find(layer.name);
-					file_keys->second.minzoom = z;
-					file_keys->second.maxzoom = z;
+					tilestats = layermap.find(layer.name);
+					tilestats->second.minzoom = z;
+					tilestats->second.maxzoom = z;
 				}
 
 				// To keep attributes in their original order instead of alphabetical
@@ -282,7 +282,7 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 
 					if (fa != attributes.end()) {
 						outlayer.tag(outfeature, k, fa->second.first);
-						add_to_file_keys(file_keys->second.file_keys, k, fa->second.second);
+						add_to_tilestats(tilestats->second.tilestats, k, fa->second.second);
 						attributes.erase(fa);
 					}
 				}
@@ -300,19 +300,19 @@ void append_tile(std::string message, int z, unsigned x, unsigned y, std::map<st
 				features_added++;
 				outlayer.features.push_back(outfeature);
 
-				if (z < file_keys->second.minzoom) {
-					file_keys->second.minzoom = z;
+				if (z < tilestats->second.minzoom) {
+					tilestats->second.minzoom = z;
 				}
-				if (z > file_keys->second.maxzoom) {
-					file_keys->second.maxzoom = z;
+				if (z > tilestats->second.maxzoom) {
+					tilestats->second.maxzoom = z;
 				}
 
 				if (feat.type == mvt_point) {
-					file_keys->second.points++;
+					tilestats->second.points++;
 				} else if (feat.type == mvt_linestring) {
-					file_keys->second.lines++;
+					tilestats->second.lines++;
 				} else if (feat.type == mvt_polygon) {
-					file_keys->second.polygons++;
+					tilestats->second.polygons++;
 				}
 			}
 		}
diff --git a/tile.cpp b/tile.cpp
index 5b9f8ef2..2e5cd7b0 100644
--- a/tile.cpp
+++ b/tile.cpp
@@ -1822,7 +1822,7 @@ void add_tilestats(std::string const &layername, int z, std::vector<std::map<std
 		exit(EXIT_IMPOSSIBLE);
 	}
 
-	add_to_file_keys(fk->second.file_keys, key, val);
+	add_to_tilestats(fk->second.tilestats, key, val);
 }
 
 void preserve_attribute(attribute_op op, serial_feature &, char *stringpool, long long *pool_off, std::string &key, serial_val &val, partial &p) {