diff --git a/src/header/bits_pthread/mod.rs b/src/header/bits_pthread/mod.rs
index ce21b6a3fa..dfaf07a53f 100644
--- a/src/header/bits_pthread/mod.rs
+++ b/src/header/bits_pthread/mod.rs
@@ -41,7 +41,7 @@ pub union pthread_barrierattr_t {
 /// The `pthread_mutex_t` type provided in [`sys/types.h`](crate::header::sys_types).
 #[repr(C)]
 pub union pthread_mutex_t {
-    __relibc_internal_size: [c_uchar; 12],
+    __relibc_internal_size: [c_uchar; 16],
     __relibc_internal_align: c_int,
 }
 /// The `pthread_mutexattr_t` type provided in [`sys/types.h`](crate::header::sys_types).