diff --git a/power/ReadVcdActivities.cc b/power/ReadVcdActivities.cc
index fec6b2d3..894525b0 100644
--- a/power/ReadVcdActivities.cc
+++ b/power/ReadVcdActivities.cc
@@ -29,6 +29,7 @@
 
 namespace sta {
 
+using std::abs;
 using std::min;
 using std::to_string;