diff --git a/PDP18B/pdp18b_stddev.c b/PDP18B/pdp18b_stddev.c
index 3748b1c7..ecb96087 100644
--- a/PDP18B/pdp18b_stddev.c
+++ b/PDP18B/pdp18b_stddev.c
@@ -482,7 +482,7 @@ int32 clk_cosched (int32 wait)
 {
 int32 t;
 
-t = sim_is_active (&clk_unit);
+t = sim_activate_time (&clk_unit);
 return (t? t - 1: wait);
 }
 
diff --git a/PDP8/pdp8_clk.c b/PDP8/pdp8_clk.c
index 8f38affe..25ce62d6 100644
--- a/PDP8/pdp8_clk.c
+++ b/PDP8/pdp8_clk.c
@@ -157,7 +157,7 @@ int32 clk_cosched (int32 wait)
 {
 int32 t;
 
-t = sim_is_active (&clk_unit);
+t = sim_activate_time (&clk_unit);
 return (t? t - 1: wait);
 }