diff --git a/histogram.cpp b/histogram.cpp
index 5867495..52c06d3 100644
--- a/histogram.cpp
+++ b/histogram.cpp
@@ -3,7 +3,7 @@
 #include <vector>
 using namespace std;
 
-void find_minmax(const vector<double> &numbers, double &min, double &max)
+void find_minmax( vector<double> numbers, double &min, double &max)
 {
     min = numbers[0];
     max = numbers[0];