diff --git a/include/bits/signal.h b/include/bits/signal.h
new file mode 100644
index 0000000000000000000000000000000000000000..46cc2553eda4c860054838f6c48ea5874aba25a6
--- /dev/null
+++ b/include/bits/signal.h
@@ -0,0 +1,8 @@
+#ifndef _BITS_SIGNAL_H
+#define _BITS_SIGNAL_H
+
+#define SIG_DFL ((void (*)(int))0)
+#define SIG_IGN ((void (*)(int))1)
+#define SIG_ERR ((void (*)(int))-1)
+
+#endif // _BITS_SIGNAL_H
diff --git a/src/header/signal/cbindgen.toml b/src/header/signal/cbindgen.toml
index cbcd1afc481f423f9882f7a483573bbd54b495ab..73a7c9e41775be6be27e601f7a3906c25e6c5c84 100644
--- a/src/header/signal/cbindgen.toml
+++ b/src/header/signal/cbindgen.toml
@@ -1,5 +1,6 @@
 sys_includes = ["stdint.h", "sys/types.h"]
 include_guard = "_SIGNAL_H"
+trailer = "#include <bits/signal.h>"
 language = "C"
 style = "Tag"
 no_includes = true
diff --git a/src/header/signal/mod.rs b/src/header/signal/mod.rs
index d8cb65cb61162958d1fafe7705b5887d2512f42d..0ce5ec9d490e6d9f5b7df41df305ff6ff3086289 100644
--- a/src/header/signal/mod.rs
+++ b/src/header/signal/mod.rs
@@ -21,9 +21,9 @@ pub mod sys;
 
 type SigSet = BitSet<[c_ulong; 1]>;
 
-pub const SIG_DFL: usize = 0;
-pub const SIG_IGN: usize = 1;
-pub const SIG_ERR: isize = -1;
+pub (crate) const SIG_DFL: usize = 0;
+pub (crate) const SIG_IGN: usize = 1;
+pub (crate) const SIG_ERR: isize = -1;
 
 pub const SIG_BLOCK: c_int = 0;
 pub const SIG_UNBLOCK: c_int = 1;