diff --git a/libc/bionic/err.c b/libc/bionic/err.c
index 535b7e1..84a3d85 100644
--- a/libc/bionic/err.c
+++ b/libc/bionic/err.c
@@ -34,7 +34,7 @@
 #include <stdarg.h>
 #include <errno.h>
 
-extern char *__progname;
+extern const char* __progname;
 
 __noreturn void
 err(int eval, const char *fmt, ...)