diff --git a/numpy/core/src/multiarray/descriptor.c b/numpy/core/src/multiarray/descriptor.c
index 5182a28dd542..595702fcf7fd 100644
--- a/numpy/core/src/multiarray/descriptor.c
+++ b/numpy/core/src/multiarray/descriptor.c
@@ -447,8 +447,8 @@ _convert_from_array_descr(PyObject *obj, int align)
         else if (PyTuple_Check(name)) {
             if (PyTuple_GET_SIZE(name) != 2) {
                 PyErr_Format(PyExc_TypeError, 
-				"If a tuple, the first element of a field tuple must have \
-				two elements, not %d",
+				"If a tuple, the first element of a field tuple must have "
+				"two elements, not %zd",
 			       	PyTuple_GET_SIZE(name));
                 goto fail;
             }