diff --git a/libguile/scmsigs.c b/libguile/scmsigs.c
index 22e211de3..7fd3fd8f1 100644
--- a/libguile/scmsigs.c
+++ b/libguile/scmsigs.c
@@ -760,7 +760,7 @@ scm_i_close_signal_pipe()
   scm_i_pthread_mutex_lock (&signal_delivery_thread_mutex);
 
 #if SCM_USE_PTHREAD_THREADS
-  if (scm_i_signal_delivery_thread != NULL)
+  if (scm_is_true (scm_i_signal_delivery_thread))
     close (signal_pipe[1]);
 #endif