diff --git a/internal/ceres/covariance_impl.cc b/internal/ceres/covariance_impl.cc
index d7a7c07..1679f23 100644
--- a/internal/ceres/covariance_impl.cc
+++ b/internal/ceres/covariance_impl.cc
@@ -617,7 +617,7 @@
       SPQR_ORDERING_BESTAMD,
       options_.column_pivot_threshold < 0 ? SPQR_DEFAULT_TOL
                                           : options_.column_pivot_threshold,
-      cholmod_jacobian.ncol,
+      static_cast<int64_t>(cholmod_jacobian.ncol),
       &cholmod_jacobian,
       &R,
       &permutation,