diff --git a/src/mlpack/methods/preprocess/preprocess_scale_main.cpp b/src/mlpack/methods/preprocess/preprocess_scale_main.cpp
index dadd2554a7..cf68b8408c 100644
--- a/src/mlpack/methods/preprocess/preprocess_scale_main.cpp
+++ b/src/mlpack/methods/preprocess/preprocess_scale_main.cpp
@@ -13,6 +13,7 @@
 #include <mlpack/core/util/cli.hpp>
 #include <mlpack/core/util/mlpack_main.hpp>
 #include <mlpack/core/math/random.hpp>
+#include <mlpack/core/math/ccov.hpp>
 #include <mlpack/core/data/scaler_methods/max_abs_scaler.hpp>
 #include <mlpack/core/data/scaler_methods/mean_normalization.hpp>
 #include <mlpack/core/data/scaler_methods/min_max_scaler.hpp>