diff --git a/libc/upstream-openbsd/android/include/openbsd-compat.h b/libc/upstream-openbsd/android/include/openbsd-compat.h
index afd1077..878f71c 100644
--- a/libc/upstream-openbsd/android/include/openbsd-compat.h
+++ b/libc/upstream-openbsd/android/include/openbsd-compat.h
@@ -19,6 +19,8 @@
 #define _BSD_SOURCE
 #include <sys/cdefs.h>
 
+#include <unistd.h> // For environ.
+
 #include <stddef.h> // For size_t.
 
 #include <sys/random.h> // For getentropy.