diff --git a/psycopg/bytes_format.c b/psycopg/bytes_format.c
index 6d12d6c7..206e870d 100644
--- a/psycopg/bytes_format.c
+++ b/psycopg/bytes_format.c
@@ -237,7 +237,7 @@ Bytes_Format(PyObject *format, PyObject *args)
             default:
                 PyErr_Format(PyExc_ValueError,
                   "unsupported format character '%c' (0x%x) "
-                  "at index %zd",
+                  "at index " FORMAT_CODE_PY_SSIZE_T,
                   c, c,
                   (Py_ssize_t)(fmt - 1 -
                                Bytes_AsString(format)));
diff --git a/psycopg/lobject_int.c b/psycopg/lobject_int.c
index d6ebd44e..b78b4a9b 100644
--- a/psycopg/lobject_int.c
+++ b/psycopg/lobject_int.c
@@ -203,7 +203,7 @@ lobject_write(lobjectObject *self, const char *buf, size_t len)
     PGresult *pgres = NULL;
     char *error = NULL;
 
-    Dprintf("lobject_writing: fd = %d, len = " FORMAT_CODE_PY_SSIZE_T,
+    Dprintf("lobject_writing: fd = %d, len = " FORMAT_CODE_SIZE_T,
             self->fd, len);
 
     Py_BEGIN_ALLOW_THREADS;
@@ -338,7 +338,7 @@ lobject_truncate(lobjectObject *self, size_t len)
     PGresult *pgres = NULL;
     char *error = NULL;
 
-    Dprintf("lobject_truncate: fd = %d, len = " FORMAT_CODE_PY_SSIZE_T,
+    Dprintf("lobject_truncate: fd = %d, len = " FORMAT_CODE_SIZE_T,
             self->fd, len);
 
     Py_BEGIN_ALLOW_THREADS;