diff --git a/libc/bionic/pthread_key.cpp b/libc/bionic/pthread_key.cpp
index 27eab27..b47ef22 100644
--- a/libc/bionic/pthread_key.cpp
+++ b/libc/bionic/pthread_key.cpp
@@ -26,6 +26,7 @@
  * SUCH DAMAGE.
  */
 
+#include <errno.h>
 #include <pthread.h>
 
 #include "private/bionic_tls.h"