diff --git a/mbtiles.cpp b/mbtiles.cpp
index f24c91dd..0c89ef34 100644
--- a/mbtiles.cpp
+++ b/mbtiles.cpp
@@ -101,19 +101,6 @@ sqlite3 *mbtiles_open(char *dbname, char **argv, int forcetable) {
 	return outdb;
 }
 
-unsigned long long fnv1a(std::string const &s) {
-	// Store tiles by a hash of their contents (fnv1a 64-bit)
-	// http://www.isthe.com/chongo/tech/comp/fnv/
-	const unsigned long long fnv_offset_basis = 14695981039346656037u;
-	const unsigned long long fnv_prime = 1099511628211u;
-	unsigned long long h = fnv_offset_basis;
-	for (size_t i = 0; i < s.size(); i++) {
-		h ^= (unsigned char) s[i];
-		h *= fnv_prime;
-	}
-	return h;
-}
-
 void mbtiles_write_tile(sqlite3 *outdb, int z, int tx, int ty, const char *data, int size) {
 	std::string hash = std::to_string(fnv1a(std::string(data, size)));
 
diff --git a/mbtiles.hpp b/mbtiles.hpp
index b1837668..8863df60 100644
--- a/mbtiles.hpp
+++ b/mbtiles.hpp
@@ -78,6 +78,4 @@ std::map<std::string, layermap_entry> merge_layermaps(std::vector<std::map<std::
 
 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);
-
 #endif
diff --git a/text.cpp b/text.cpp
index 0d0f0460..21dc0b02 100644
--- a/text.cpp
+++ b/text.cpp
@@ -184,3 +184,31 @@ char *dtoa_milo(double val) {
 	}
 	return dup;
 }
+
+unsigned long long fnv1a(std::string const &s) {
+	// Store tiles by a hash of their contents (fnv1a 64-bit)
+	// http://www.isthe.com/chongo/tech/comp/fnv/
+	const unsigned long long fnv_offset_basis = 14695981039346656037u;
+	const unsigned long long fnv_prime = 1099511628211u;
+	unsigned long long h = fnv_offset_basis;
+	for (size_t i = 0; i < s.size(); i++) {
+		h ^= (unsigned char) s[i];
+		h *= fnv_prime;
+	}
+	return h;
+}
+
+unsigned long long fnv1a(const char *s, char additional) {
+	// Store tiles by a hash of their contents (fnv1a 64-bit)
+	// http://www.isthe.com/chongo/tech/comp/fnv/
+	const unsigned long long fnv_offset_basis = 14695981039346656037u;
+	const unsigned long long fnv_prime = 1099511628211u;
+	unsigned long long h = fnv_offset_basis;
+	for (size_t i = 0; s[i] != '\0'; i++) {
+		h ^= (unsigned char) s[i];
+		h *= fnv_prime;
+	}
+	h ^= (unsigned char) additional;
+	h *= fnv_prime;
+	return h;
+}
diff --git a/text.hpp b/text.hpp
index 94e41f2c..930aa227 100644
--- a/text.hpp
+++ b/text.hpp
@@ -8,5 +8,7 @@ const char *utf8_next(const char *s, long *c);
 std::string truncate16(std::string const &s, size_t runes);
 int integer_zoom(std::string where, std::string text);
 std::string format_commandline(int argc, char **argv);
+unsigned long long fnv1a(std::string const &s);
+unsigned long long fnv1a(const char *s, char additional);
 
 #endif