diff --git a/util/PatternMatch.cc b/util/PatternMatch.cc
index b918a9e6..b4db32be 100644
--- a/util/PatternMatch.cc
+++ b/util/PatternMatch.cc
@@ -15,7 +15,7 @@
 // along with this program.  If not, see <https://www.gnu.org/licenses/>.
 
 #include "PatternMatch.hh"
-
+#include <string.h>
 #include <tcl.h>
 
 namespace sta {