diff --git a/tests/unit/data_generator.hpp b/tests/unit/data_generator.hpp
index e4e7dfa85..d8342b634 100644
--- a/tests/unit/data_generator.hpp
+++ b/tests/unit/data_generator.hpp
@@ -68,7 +68,7 @@ std::vector<size_t> unravel(size_t flat_index, const Dims& dims) {
 }
 
 template <class Dims>
-static size_t flat_size(const Dims& dims) {
+size_t flat_size(const Dims& dims) {
     size_t n = 1;
     for (auto d: dims) {
         n *= d;