diff --git a/python-package/xgboost/core.py b/python-package/xgboost/core.py
index cd028ba0bedf..d0ffb7957336 100644
--- a/python-package/xgboost/core.py
+++ b/python-package/xgboost/core.py
@@ -2307,7 +2307,7 @@ def inplace_predict(
                     _array_interface(csr.indptr),
                     _array_interface(csr.indices),
                     _array_interface(csr.data),
-                    ctypes.c_size_t(csr.shape[1]),
+                    c_bst_ulong(csr.shape[1]),
                     from_pystr_to_cstr(json.dumps(args)),
                     p_handle,
                     ctypes.byref(shape),
diff --git a/python-package/xgboost/data.py b/python-package/xgboost/data.py
index e486fb57a5f5..775eedd5776f 100644
--- a/python-package/xgboost/data.py
+++ b/python-package/xgboost/data.py
@@ -103,7 +103,7 @@ def _from_scipy_csr(
             _array_interface(data.indptr),
             _array_interface(data.indices),
             _array_interface(data.data),
-            ctypes.c_size_t(data.shape[1]),
+            c_bst_ulong(data.shape[1]),
             config,
             ctypes.byref(handle),
         )