diff --git a/liblogdiag/ld-canvas.c b/liblogdiag/ld-canvas.c
index 84aaf67..564a838 100644
--- a/liblogdiag/ld-canvas.c
+++ b/liblogdiag/ld-canvas.c
@@ -1022,11 +1022,16 @@ is_object_selected (LdCanvas *self, LdDiagramObject *object)
 static LdSymbol *
 resolve_diagram_symbol (LdCanvas *self, LdDiagramSymbol *diagram_symbol)
 {
+	LdSymbol *symbol;
+	gchar *klass;
+
 	if (!self->priv->library)
 		return NULL;
 
-	return ld_library_find_symbol (self->priv->library,
-		ld_diagram_symbol_get_class (diagram_symbol));
+	klass = ld_diagram_symbol_get_class (diagram_symbol);
+	symbol = ld_library_find_symbol (self->priv->library, klass);
+	g_free (klass);
+	return symbol;
 }
 
 static gboolean
@@ -1789,8 +1794,11 @@ draw_symbol (LdDiagramSymbol *diagram_symbol, DrawData *data)
 	/* TODO: Resolve this better; draw a cross or whatever. */
 	if (!symbol)
 	{
-		g_warning ("cannot find symbol `%s' in the library",
-			ld_diagram_symbol_get_class (diagram_symbol));
+		gchar *klass;
+
+		klass = ld_diagram_symbol_get_class (diagram_symbol);
+		g_warning ("cannot find symbol `%s' in the library", klass);
+		g_free (klass);
 		return;
 	}
 
diff --git a/liblogdiag/ld-diagram-symbol.c b/liblogdiag/ld-diagram-symbol.c
index 370d6ec..8307ef4 100644
--- a/liblogdiag/ld-diagram-symbol.c
+++ b/liblogdiag/ld-diagram-symbol.c
@@ -116,10 +116,10 @@ ld_diagram_symbol_new (JsonObject *storage)
  *
  * Return value: the class of the symbol.
  */
-const gchar *
+gchar *
 ld_diagram_symbol_get_class (LdDiagramSymbol *self)
 {
-	const gchar *klass;
+	gchar *klass;
 
 	g_return_val_if_fail (LD_IS_DIAGRAM_SYMBOL (self), NULL);
 	g_object_get (self, "class", &klass, NULL);
diff --git a/liblogdiag/ld-diagram-symbol.h b/liblogdiag/ld-diagram-symbol.h
index f2e60e9..d96c0f0 100644
--- a/liblogdiag/ld-diagram-symbol.h
+++ b/liblogdiag/ld-diagram-symbol.h
@@ -53,7 +53,7 @@ struct _LdDiagramSymbolClass
 GType ld_diagram_symbol_get_type (void) G_GNUC_CONST;
 
 LdDiagramSymbol *ld_diagram_symbol_new (JsonObject *storage);
-const gchar *ld_diagram_symbol_get_class (LdDiagramSymbol *self);
+gchar *ld_diagram_symbol_get_class (LdDiagramSymbol *self);
 void ld_diagram_symbol_set_class (LdDiagramSymbol *self, const gchar *klass);