diff --git a/pandas/_libs/writers.pyx b/pandas/_libs/writers.pyx
index 9e95dea979577..ebf98232da58b 100644
--- a/pandas/_libs/writers.pyx
+++ b/pandas/_libs/writers.pyx
@@ -36,7 +36,7 @@ def write_csv_rows(
     """
     # In crude testing, N>100 yields little marginal improvement
     cdef:
-        Py_ssize_t i, j, k = len(data_index), N = 100, ncols = len(cols)
+        Py_ssize_t i, j = 0, k = len(data_index), N = 100, ncols = len(cols)
         list rows
 
     # pre-allocate rows