diff --git a/core/device.cpp b/core/device.cpp
index 8096d1efa..05646df66 100644
--- a/core/device.cpp
+++ b/core/device.cpp
@@ -286,12 +286,20 @@ extern "C" uint32_t fp_get_diveid(struct fingerprint_table *table, unsigned int
 	return table->fingerprints[i].fdiveid;
 }
 
-extern "C" char *fp_get_data(struct fingerprint_table *table, unsigned int i)
+static char to_hex_digit(unsigned char d)
+{
+	return d <= 9 ? d + '0' : d - 10 + 'a';
+}
+
+std::string fp_get_data(struct fingerprint_table *table, unsigned int i)
 {
 	if (!table || i >= table->fingerprints.size())
-		return 0;
+		return std::string();
 	struct fingerprint_record *fpr = &table->fingerprints[i];
-	// fromRawData() avoids one copy of the raw_data
-	QByteArray hex = QByteArray::fromRawData((char *)fpr->raw_data, fpr->fsize).toHex();
-	return strdup(hex.constData());
+	std::string res(' ', fpr->fsize * 2);
+	for (unsigned int i = 0; i < fpr->fsize; ++i) {
+		res[2 * i] = to_hex_digit((fpr->raw_data[i] >> 4) & 0xf);
+		res[2 * i + 1] = to_hex_digit(fpr->raw_data[i] & 0xf);
+	}
+	return res;
 }
diff --git a/core/device.h b/core/device.h
index 2abd0aa14..147f56e1e 100644
--- a/core/device.h
+++ b/core/device.h
@@ -54,7 +54,6 @@ extern uint32_t fp_get_model(struct fingerprint_table *table, unsigned int i);
 extern uint32_t fp_get_serial(struct fingerprint_table *table, unsigned int i);
 extern uint32_t fp_get_deviceid(struct fingerprint_table *table, unsigned int i);
 extern uint32_t fp_get_diveid(struct fingerprint_table *table, unsigned int i);
-extern char *fp_get_data(struct fingerprint_table *table, unsigned int i);
 
 extern int is_default_dive_computer_device(const char *);
 
@@ -100,6 +99,8 @@ struct fingerprint_table {
 	std::vector<fingerprint_record> fingerprints;
 };
 
+std::string fp_get_data(struct fingerprint_table *table, unsigned int i);
+
 #endif
 
 #endif // DEVICE_H
diff --git a/core/save-git.cpp b/core/save-git.cpp
index 78e0b0ec3..4112b217e 100644
--- a/core/save-git.cpp
+++ b/core/save-git.cpp
@@ -881,14 +881,12 @@ static void save_one_device(struct membuffer *b, const struct device *d)
 
 static void save_one_fingerprint(struct membuffer *b, int i)
 {
-	char *fp_data = fp_get_data(&fingerprint_table, i);
 	put_format(b, "fingerprint model=%08x serial=%08x deviceid=%08x diveid=%08x data=\"%s\"\n",
 		   fp_get_model(&fingerprint_table, i),
 		   fp_get_serial(&fingerprint_table, i),
 		   fp_get_deviceid(&fingerprint_table, i),
 		   fp_get_diveid(&fingerprint_table, i),
-		   fp_data);
-	free(fp_data);
+		   fp_get_data(&fingerprint_table, i).c_str());
 }
 
 static void save_settings(git_repository *repo, struct dir *tree)
diff --git a/core/save-xml.cpp b/core/save-xml.cpp
index b70c52587..89818d439 100644
--- a/core/save-xml.cpp
+++ b/core/save-xml.cpp
@@ -620,14 +620,12 @@ static void save_one_device(struct membuffer *b, const struct device *d)
 
 static void save_one_fingerprint(struct membuffer *b, int i)
 {
-	char *data = fp_get_data(&fingerprint_table, i);
 	put_format(b, "<fingerprint model='%08x' serial='%08x' deviceid='%08x' diveid='%08x' data='%s'/>\n",
 		   fp_get_model(&fingerprint_table, i),
 		   fp_get_serial(&fingerprint_table, i),
 		   fp_get_deviceid(&fingerprint_table, i),
 		   fp_get_diveid(&fingerprint_table, i),
-		   data);
-	free(data);
+		   fp_get_data(&fingerprint_table, i).c_str());
 }
 
 extern "C" int save_dives(const char *filename)