diff --git a/cpp/pmtiles.hpp b/cpp/pmtiles.hpp
index 0b3de55..1bfeaf7 100644
--- a/cpp/pmtiles.hpp
+++ b/cpp/pmtiles.hpp
@@ -311,14 +311,14 @@ void rotate(int64_t n, int64_t &x, int64_t &y, int64_t rx, int64_t ry) {
 }
 
 zxy t_on_level(uint8_t z, uint64_t pos) {
-	int64_t n = 1 << z;
+	int64_t n = 1LL << z;
 	int64_t rx, ry, s, t = pos;
 	int64_t tx = 0;
 	int64_t ty = 0;
 
 	for (s = 1; s < n; s *= 2) {
-		rx = 1 & (t / 2);
-		ry = 1 & (t ^ rx);
+		rx = 1LL & (t / 2);
+		ry = 1LL & (t ^ rx);
 		rotate(s, tx, ty, rx, ry);
 		tx += s * rx;
 		ty += s * ry;
@@ -385,28 +385,33 @@ entryv3 find_tile(const std::vector<entryv3> &entries, uint64_t tile_id) {
 
 inline zxy tileid_to_zxy(uint64_t tileid) {
 	uint64_t acc = 0;
-	uint8_t t_z = 0;
-	while (true) {
+	for (uint8_t t_z = 0; t_z < 32; t_z++) {
 		uint64_t num_tiles = (1LL << t_z) * (1LL << t_z);
 		if (acc + num_tiles > tileid) {
 			return t_on_level(t_z, tileid - acc);
 		}
 		acc += num_tiles;
-		t_z++;
 	}
+	throw std::overflow_error("tile zoom exceeds 64-bit limit");
 }
 
 inline uint64_t zxy_to_tileid(uint8_t z, uint32_t x, uint32_t y) {
+	if (z > 31) {
+		throw std::overflow_error("tile zoom exceeds 64-bit limit");
+	}
+	if (x > (1 << z) - 1 || y > (1 << z) - 1) {
+		throw std::overflow_error("tile x/y outside zoom level bounds");
+	}
 	uint64_t acc = 0;
 	for (uint8_t t_z = 0; t_z < z; t_z++) acc += (1LL << t_z) * (1LL << t_z);
-	int64_t n = 1 << z;
+	int64_t n = 1LL << z;
 	int64_t rx, ry, s, d = 0;
 	int64_t tx = x;
 	int64_t ty = y;
 	for (s = n / 2; s > 0; s /= 2) {
 		rx = (tx & s) > 0;
 		ry = (ty & s) > 0;
-		d += s * s * ((3 * rx) ^ ry);
+		d += s * s * ((3LL * rx) ^ ry);
 		rotate(s, tx, ty, rx, ry);
 	}
 	return acc + d;
diff --git a/cpp/test.cpp b/cpp/test.cpp
index 90e8217..37afb5e 100644
--- a/cpp/test.cpp
+++ b/cpp/test.cpp
@@ -46,7 +46,7 @@ MU_TEST(test_zxy_to_tileid) {
 }
 
 MU_TEST(test_roundtrip) {
-	for (int z = 0; z < 25; z++) {
+	for (int z = 0; z < 32; z++) {
 		uint64_t dim = (1 << z) - 1;
 		auto tl = tileid_to_zxy(zxy_to_tileid(z, 0, 0));
 		mu_check(tl.z == z);
@@ -65,6 +65,41 @@ MU_TEST(test_roundtrip) {
 		mu_check(br.x == dim);
 		mu_check(br.y == dim);
 	}
+
+	bool caught = false;
+	try {
+		tileid_to_zxy(18446744073709551615ULL);
+	} catch (const std::runtime_error &e) {
+		caught = true;
+	}
+
+	mu_check(caught);
+
+	caught = false;
+	try {
+		zxy_to_tileid(32, 0, 0);
+	} catch (const std::runtime_error &e) {
+		caught = true;
+	}
+
+	mu_check(caught);
+
+	caught = false;
+	try {
+		zxy_to_tileid(0, 1, 1);
+	} catch (const std::runtime_error &e) {
+		caught = true;
+	}
+
+	mu_check(caught);
+
+	caught = false;
+	try {
+		zxy_to_tileid(31, 2147483647ULL + 1, 2147483647ULL + 1);
+	} catch (const std::runtime_error &e) {
+		caught = true;
+	}
+	mu_check(caught);
 }
 
 MU_TEST(test_serialize_directory) {