diff --git a/folks/debug.vala b/folks/debug.vala
index 51f119d..f73879d 100644
--- a/folks/debug.vala
+++ b/folks/debug.vala
@@ -332,7 +332,7 @@ public class Folks.Debug : Object
     {
       /* FIXME: store the va_list temporarily to work around bgo#638308 */
       var valist = va_list ();
-      string output = format.vprintf (valist);
+      string output = format.vprintf (valist.arg());
       g_log (domain, level, "%s%s", this._indentation_string, output);
     }
 
@@ -374,7 +374,7 @@ public class Folks.Debug : Object
 
       /* FIXME: store the va_list temporarily to work around bgo#638308 */
       var valist = va_list ();
-      string output = format.vprintf (valist);
+      string output = format.vprintf (valist.arg());
       this.print_line (domain, level, wrapper_format, output);
     }
 
