diff --git a/tests/cpp/helpers.cc b/tests/cpp/helpers.cc
index c91a74ff5..741a228cf 100644
--- a/tests/cpp/helpers.cc
+++ b/tests/cpp/helpers.cc
@@ -38,12 +38,6 @@ bool FileExists(const std::string& filename) {
   return stat(filename.c_str(), &st) == 0;
 }
 
-int64_t GetFileSize(const std::string& filename) {
-  struct stat st;
-  stat(filename.c_str(), &st);
-  return st.st_size;
-}
-
 void CreateSimpleTestData(const std::string& filename) {
   CreateBigTestData(filename, 6);
 }
diff --git a/tests/cpp/helpers.h b/tests/cpp/helpers.h
index 6c7ae68d8..00c38e452 100644
--- a/tests/cpp/helpers.h
+++ b/tests/cpp/helpers.h
@@ -50,8 +50,6 @@ Float RelError(Float l, Float r) {
 
 bool FileExists(const std::string& filename);
 
-int64_t GetFileSize(const std::string& filename);
-
 void CreateSimpleTestData(const std::string& filename);
 
 // Create a libsvm format file with 3 entries per-row. `zero_based` specifies whether it's