diff --git a/core/string.cpp b/core/string.cpp
index 4584f931..ddd1fc85 100644
--- a/core/string.cpp
+++ b/core/string.cpp
@@ -2,25 +2,15 @@
  * Copyright 2015 (c) Anna Schumaker.
  */
 #include <core/string.h>
-#include <glib.h>
-#include <sstream>
 
 #define O_MINUTES (60)
 #define O_HOURS   (60 * O_MINUTES)
 #define O_DAYS    (24 * O_HOURS)
 
 
-const std::string string :: sec2str(unsigned int sec)
+gchar *string_sec2str(unsigned int sec)
 {
-	std::stringstream ss;
-	unsigned int minutes = sec / 60;
-	unsigned int seconds = sec % 60;
-
-	ss << minutes << ":";
-	if (seconds < 10)
-		ss << "0";
-	ss << seconds;
-	return ss.str();
+	return g_strdup_printf("%u:%02u", sec / 60, sec % 60);
 }
 
 static const std::string _time_detail(unsigned int value,
diff --git a/gui/gst.cpp b/gui/gst.cpp
index b605522c..2af30bef 100644
--- a/gui/gst.cpp
+++ b/gui/gst.cpp
@@ -58,6 +58,7 @@ public:
 	void load(Track *track)
 	{
 		gchar *uri = gst_filename_to_uri(track->path().c_str(), NULL);
+		gchar *len = string_sec2str(track->length());
 
 		gst_change_state(GST_STATE_NULL);
 		g_object_set(G_OBJECT(gst_player), "uri", uri, NULL);
@@ -66,7 +67,8 @@ public:
 		set_markup(o_album,  "x-large", "From: " + track->album()->name());
 		set_markup(o_artist, "x-large",   "By: " + track->artist()->name());
 		set_markup(o_title, "xx-large", track->name());
-		o_duration->set_text(string :: sec2str(track->length()));
+		o_duration->set_text(len);
+		g_free(len);
 
 		plist :: track_loaded(track);
 	}
@@ -181,9 +183,12 @@ static void on_pause_enabled()
 
 static bool on_timeout()
 {
-	o_position->set_text(string :: sec2str(audio :: position() / GST_SECOND));
+	gchar *pos = string_sec2str(audio :: position() / GST_SECOND);
+
 	o_progress->set_upper(audio :: duration());
 	o_progress->set_value(audio :: position());
+	o_position->set_text(pos);
+	g_free(pos);
 	return true;
 }
 
diff --git a/gui/queue/model.cpp b/gui/queue/model.cpp
index b652ef9f..94bd8bc5 100644
--- a/gui/queue/model.cpp
+++ b/gui/queue/model.cpp
@@ -96,6 +96,7 @@ void QueueModel::get_value_vfunc(const Gtk::TreeIter &iter, int column,
 				     Glib::ValueBase &value) const
 {
 	Track *track;
+	gchar *str;
 
 	if (!check_iter_validity(iter) ||
 	     column > get_n_columns_vfunc())
@@ -109,7 +110,10 @@ void QueueModel::get_value_vfunc(const Gtk::TreeIter &iter, int column,
 	case 1:
 		return set_val(track->name(), value);
 	case 2:
-		return set_val(string :: sec2str(track->length()), value);
+		str = string_sec2str(track->length());
+		set_val(Glib::ustring(str), value);
+		g_free(str);
+		return;
 	case 3:
 		return set_val(track->artist()->name(), value);
 	case 4:
diff --git a/include/core/string.h b/include/core/string.h
index 84eaa492..1e80ef59 100644
--- a/include/core/string.h
+++ b/include/core/string.h
@@ -4,6 +4,7 @@
 #ifndef OCARINA_CORE_STRING_H
 #define OCARINA_CORE_STRING_H
 
+#include <glib.h>
 #include <string>
 
 /**
@@ -12,13 +13,6 @@
 namespace string
 {
 
-	/**
-	 * Convert from seconds to a time string.
-	 * @param  sec  Number of seconds.
-	 * @return A string in mm:ss format.
-	 */
-	const std::string sec2str(unsigned int);
-
 	/**
 	 * Convert from seconds to a detailed time string.
 	 * @param  sec  Number of seconds.
@@ -37,4 +31,10 @@ namespace string
 }
 
 
+/*
+ * Convert number of seconds into a string with format mm:ss.
+ * This function allocates a new string that MUST be freed with g_free().
+ */
+gchar *string_sec2str(unsigned int);
+
 #endif /* OCARINA_CORE_STRING_H */
diff --git a/tests/core/string.cpp b/tests/core/string.cpp
index 38b4d49b..30f19491 100644
--- a/tests/core/string.cpp
+++ b/tests/core/string.cpp
@@ -5,21 +5,29 @@
 #include <core/string.h>
 #include "test.h"
 
+static char buf[6];
+
+static inline char *swap(gchar *res)
+{
+	strcpy(buf, res);
+	g_free(res);
+	return buf;
+}
 
 void test_sec2str()
 {
-	test_equal(string :: sec2str(0),    "0:00");
-	test_equal(string :: sec2str(5),    "0:05");
-	test_equal(string :: sec2str(10),   "0:10");
-	test_equal(string :: sec2str(60),   "1:00");
-	test_equal(string :: sec2str(65),   "1:05");
-	test_equal(string :: sec2str(75),   "1:15");
-	test_equal(string :: sec2str(600), "10:00");
-	test_equal(string :: sec2str(605), "10:05");
-	test_equal(string :: sec2str(615), "10:15");
-	test_equal(string :: sec2str(660), "11:00");
-	test_equal(string :: sec2str(665), "11:05");
-	test_equal(string :: sec2str(675), "11:15");
+	test_equal(swap(string_sec2str(0)),    "0:00");
+	test_equal(swap(string_sec2str(5)),    "0:05");
+	test_equal(swap(string_sec2str(10)),   "0:10");
+	test_equal(swap(string_sec2str(60)),   "1:00");
+	test_equal(swap(string_sec2str(65)),   "1:05");
+	test_equal(swap(string_sec2str(75)),   "1:15");
+	test_equal(swap(string_sec2str(600)), "10:00");
+	test_equal(swap(string_sec2str(605)), "10:05");
+	test_equal(swap(string_sec2str(615)), "10:15");
+	test_equal(swap(string_sec2str(660)), "11:00");
+	test_equal(swap(string_sec2str(665)), "11:05");
+	test_equal(swap(string_sec2str(675)), "11:15");
 }
 
 void test_sec2str_detailed()