diff --git a/power/Power.tcl b/power/Power.tcl
index c322f565..7397f78f 100644
--- a/power/Power.tcl
+++ b/power/Power.tcl
@@ -237,7 +237,11 @@ proc set_power_activity { args } {
     set ports [get_ports_error "input_ports" $keys(-input_ports)]
     foreach port $ports {
       if { [get_property $port "direction"] == "input" } {
-	set_power_input_port_activity $port $activity $duty
+	if { [sta::is_clock_src [sta::get_port_pin $port]] } {
+          sta_warn 303 "activity cannot be set on clock ports."
+        } else {
+          set_power_input_port_activity $port $activity $duty
+        }
       }
     }
   }
diff --git a/tcl/StaTcl.i b/tcl/StaTcl.i
index 8a055209..9b096071 100644
--- a/tcl/StaTcl.i
+++ b/tcl/StaTcl.i
@@ -2393,6 +2393,13 @@ find_pin(const char *path_name)
   return cmdLinkedNetwork()->findPin(path_name);
 }
 
+Pin *
+get_port_pin(const Port *port)
+{
+  Network *network = cmdLinkedNetwork();
+  return network->findPin(network->topInstance(), port);
+}
+
 TmpPinSeq *
 find_pins_matching(const char *pattern,
 		   bool regexp,