diff --git a/vpi/vcd_priv2.cc b/vpi/vcd_priv2.cc
index 2b0c59205..1fe4bc43b 100644
--- a/vpi/vcd_priv2.cc
+++ b/vpi/vcd_priv2.cc
@@ -21,6 +21,7 @@
 # include  <map>
 # include  <set>
 # include  <string>
+# include  <pthread.h>
 # include  <stdlib.h>
 # include  <string.h>
 # include  <assert.h>