diff --git a/power/ReadVcdActivities.cc b/power/ReadVcdActivities.cc
index 853ef7bd..3abaf594 100644
--- a/power/ReadVcdActivities.cc
+++ b/power/ReadVcdActivities.cc
@@ -16,6 +16,8 @@
 
 #include "ReadVcdActivities.hh"
 
+#include <inttypes.h>
+
 #include "VcdReader.hh"
 #include "Debug.hh"
 #include "Network.hh"
@@ -212,7 +214,7 @@ ReadVcdActivities::findVarActivity(const VcdValues &var_values,
   for (const VcdValue &var_value : var_values) {
     VcdTime time = var_value.time();
     char value = var_value.value(value_bit);
-    debugPrint(debug_, "read_vcd_activities", 3, " %llu %c", time, value);
+    debugPrint(debug_, "read_vcd_activities", 3, " %" PRId64 " %c", time, value);
     if (prev_value == '1')
       high_time += time - prev_time;
     if (value != prev_value)