diff --git a/src/sage/interfaces/sagespawn.pyx b/src/sage/interfaces/sagespawn.pyx
index 9041238f1d..469befbc66 100644
--- a/src/sage/interfaces/sagespawn.pyx
+++ b/src/sage/interfaces/sagespawn.pyx
@@ -228,7 +228,7 @@ class SagePtyProcess(PtyProcess):
         Check that the process eventually dies after calling
         ``terminate_async``::
 
-            sage: s.ptyproc.terminate_async(interval=0.2)
+            sage: s.ptyproc.terminate_async(interval=float(0.2))
             sage: while True:
             ....:     try:
             ....:         os.kill(s.pid, 0)