diff --git a/src/Thresholds.cpp b/src/Thresholds.cpp
index b792a9b..c40d35d 100644
--- a/src/Thresholds.cpp
+++ b/src/Thresholds.cpp
@@ -253,7 +253,7 @@
 
 bool ParseThresholdsFromAttr(
     std::vector<thresholds::Threshold> &threshold_vector,
-    const std::string &input_path, const double scale_factor)
+    const std::string &input_path, const double &scale_factor)
 {
     for (auto &type : ATTR_TYPES)
     {