diff --git a/libunwindstack/include/unwindstack/Regs.h b/libunwindstack/include/unwindstack/Regs.h
index 878ced3..1c2a81c 100644
--- a/libunwindstack/include/unwindstack/Regs.h
+++ b/libunwindstack/include/unwindstack/Regs.h
@@ -18,6 +18,7 @@
 #define _LIBUNWINDSTACK_REGS_H
 
 #include <stdint.h>
+#include <unistd.h>
 
 #include <functional>
 #include <string>