diff --git a/libc/bionic/sigemptyset.cpp b/libc/bionic/sigemptyset.cpp
index 8d8033f..58166a1 100644
--- a/libc/bionic/sigemptyset.cpp
+++ b/libc/bionic/sigemptyset.cpp
@@ -28,6 +28,7 @@
 
 #include <errno.h>
 #include <signal.h>
+#include <string.h>
 
 int sigemptyset(sigset_t* set) {
   if (set == NULL) {