diff --git a/Makefile b/Makefile
index 5de9618..5b7d4fa 100644
--- a/Makefile
+++ b/Makefile
@@ -95,7 +95,7 @@ build/o/libstrerror.rlib: build src/libstrerror.rs
 		src/libstrerror.rs
 
 build/o/libsysexits.rlib: build/include/sysexits.h
-	bindgen --default-macro-constant-type signed --use-core --formatter=none \
+	bindgen --fit-macro-constant-types --default-macro-constant-type unsigned --use-core --formatter=none \
 		build/include/sysexits.h | $(RUSTC) $(RUSTFLAGS) --crate-type lib -o $@ -
 
 # bandage solution until bindgen(1) gets stdin support