diff --git a/src/sage/doctest/util.py b/src/sage/doctest/util.py
index 972767c3b89..a337356e4ae 100644
--- a/src/sage/doctest/util.py
+++ b/src/sage/doctest/util.py
@@ -133,7 +133,7 @@ def _pid_cpu_seconds(self, pid):
         nonnegative float or raise an ``OSError``::
 
             sage: from sage.doctest.util import Timer
-            sage: cputime = 0.0
+            sage: cputime = float(0.0)
             sage: try:
             ....:     cputime = Timer()._pid_cpu_seconds(1)
             ....: except OSError: