diff --git a/histogram_internal.h b/histogram_internal.h
deleted file mode 100644
index 0698c96..0000000
--- a/histogram_internal.h
+++ /dev/null
@@ -1,8 +0,0 @@
-#ifndef HISTOGRAM_INTERNAL_H_INCLUDED
-#define HISTOGRAM_INTERNAL_H_INCLUDED
-
-#include <vector>
-
-bool find_minmax(const std::vector<double>& numbers, double& min, double& max);
-
-#endif