diff --git a/Makefile b/Makefile
index a39ac049..c7e5492f 100644
--- a/Makefile
+++ b/Makefile
@@ -73,7 +73,7 @@ tile-join: tile-join.o projection.o mbtiles.o mvt.o memfile.o dirtiles.o jsonpul
 tippecanoe-json-tool: jsontool.o jsonpull/jsonpull.o csv.o text.o geojson-loop.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
-unit: unit.o text.o sort.o mvt.o
+unit: unit.o text.o sort.o mvt.o projection.o
 	$(CXX) $(PG) $(LIBS) $(FINAL_FLAGS) $(CXXFLAGS) -o $@ $^ $(LDFLAGS) -lm -lz -lsqlite3 -lpthread
 
 tippecanoe-overzoom: overzoom.o mvt.o clip.o evaluator.o jsonpull/jsonpull.o text.o attribute.o
diff --git a/unit.cpp b/unit.cpp
index eb5eb4c7..b14e7fd1 100644
--- a/unit.cpp
+++ b/unit.cpp
@@ -3,6 +3,7 @@
 #include "text.hpp"
 #include "sort.hpp"
 #include "tile-cache.hpp"
+#include "projection.hpp"
 #include <unistd.h>
 #include <limits.h>
 
@@ -105,3 +106,19 @@ TEST_CASE("Bit reversal", "bit reversal") {
 	REQUIRE(bit_reverse(0x1234567812489BCF) == 0xF3D912481E6A2C48);
 	REQUIRE(bit_reverse(0xF3D912481E6A2C48) == 0x1234567812489BCF);
 }
+
+TEST_CASE("Projection", "projection") {
+	// troublesome point from tests/accumulate/in.json
+	long long wx36, wy36;
+	lonlat2tile(-123.948513, -81.873970, 36, &wx36, &wy36);
+	REQUIRE(wx36 == 0x27dbdc9fb);
+	REQUIRE(wy36 == 0xebc06c629);
+
+	long long wx32, wy32;
+	lonlat2tile(-123.948513, -81.873970, 32, &wx32, &wy32);
+	REQUIRE(wx32 == 0x27dbdca0);
+	REQUIRE(wy32 == 0xebc06c63);
+
+	REQUIRE(std::llround(wx36 / 16.0) == wx32);
+	REQUIRE(std::llround(wy36 / 16.0) == wy32);
+}