diff --git a/src/taptempo.f90 b/src/taptempo.f90
index 63870d5..bdbbcae 100644
--- a/src/taptempo.f90
+++ b/src/taptempo.f90
@@ -64,7 +64,7 @@ subroutine manage_command_line
                     i = i + 1
                     call get_command_argument(i, value=args)
                     read(args, *) p
-                    p = min(p, 5)
+                    p = max(0, min(p, 5))   ! 0 <= p <= 5
                 case("-r", "--reset-time")
                     i = i + 1
                     call get_command_argument(i, value=args)