diff --git a/Objects/bytesobject.c b/Objects/bytesobject.c
index 4223dc9..f9823f1 100644
--- a/Objects/bytesobject.c
+++ b/Objects/bytesobject.c
@@ -667,9 +667,6 @@
             Py_ssize_t len = 0;
             char onechar; /* For byte_converter() */
             Py_ssize_t alloc;
-#ifdef Py_DEBUG
-            char *before;
-#endif
 
             fmt++;
             if (*fmt == '%') {
@@ -981,8 +978,8 @@
                 if (res == NULL)
                     goto error;
             }
-#ifdef Py_DEBUG
-            before = res;
+#ifndef NDEBUG
+            char *before = res;
 #endif
 
             /* Write the sign if needed */
@@ -1047,7 +1044,7 @@
             }
             Py_XDECREF(temp);
 
-#ifdef Py_DEBUG
+#ifndef NDEBUG
             /* check that we computed the exact size for this write */
             assert((res - before) == alloc);
 #endif
@@ -3168,8 +3165,9 @@
 {
     /* Set all attributes before small_buffer to 0 */
     memset(writer, 0, offsetof(_PyBytesWriter, small_buffer));
-#ifdef Py_DEBUG
-    memset(writer->small_buffer, 0xCB, sizeof(writer->small_buffer));
+#ifndef NDEBUG
+    memset(writer->small_buffer, PYMEM_CLEANBYTE,
+           sizeof(writer->small_buffer));
 #endif
 }
 
@@ -3297,8 +3295,9 @@
         }
 
         writer->use_small_buffer = 0;
-#ifdef Py_DEBUG
-        memset(writer->small_buffer, 0xDB, sizeof(writer->small_buffer));
+#ifndef NDEBUG
+        memset(writer->small_buffer, PYMEM_CLEANBYTE,
+               sizeof(writer->small_buffer));
 #endif
     }
     writer->allocated = allocated;
@@ -3350,7 +3349,7 @@
     assert(size >= 0);
 
     writer->use_small_buffer = 1;
-#ifdef Py_DEBUG
+#ifndef NDEBUG
     writer->allocated = sizeof(writer->small_buffer) - 1;
     /* In debug mode, don't use the full small buffer because it is less
        efficient than bytes and bytearray objects to detect buffer underflow