diff --git a/Include/cpython/bytesobject.h b/Include/cpython/bytesobject.h
index 0af4c83b1e5bc79..f7d1338540d5038 100644
--- a/Include/cpython/bytesobject.h
+++ b/Include/cpython/bytesobject.h
@@ -5,7 +5,7 @@
 typedef struct {
     PyObject_VAR_HEAD
     Py_DEPRECATED(3.11) Py_hash_t ob_shash;
-    char ob_sval[1];
+    unsigned char ob_sval[1];
 
     /* Invariants:
      *     ob_sval contains space for 'ob_size+1' elements.