diff --git a/RayTracer/tools/Threadpool.cpp b/RayTracer/tools/Threadpool.cpp
index 1f017e1f9151855e7d30863cc91c2ed014527e64..2336571155c068c08c8e34435306df50c964b765 100644
--- a/RayTracer/tools/Threadpool.cpp
+++ b/RayTracer/tools/Threadpool.cpp
@@ -18,10 +18,10 @@ Threadpool::~Threadpool() {
 	alive = false;
 	cv.notify_all();
 
-	for (auto &thread : threads) thread.join();
+	for (auto& thread : threads) thread.join();
 }
 
-void Threadpool::queueTask(std::function<void(void)> task) {
+void Threadpool::queueTask(const std::function<void(void)>& task) {
 	std::unique_lock<std::mutex> lock(m);
 	q.emplace(task);
 	lock.unlock();
diff --git a/RayTracer/tools/Threadpool.h b/RayTracer/tools/Threadpool.h
index bc003e002997cb909f44a58a538e73d41663fb0b..55a97dc35e50701271c426628886adae33e45a63 100644
--- a/RayTracer/tools/Threadpool.h
+++ b/RayTracer/tools/Threadpool.h
@@ -13,7 +13,7 @@ class Threadpool {
 	Threadpool(size_t n);
 	~Threadpool();
 	// Add a task to the queue
-	void queueTask(std::function<void(void)> task);
+	void queueTask(const std::function<void(void)>& task);
 
    private:
 	void threading();
diff --git a/RayTracer/tools/Transformation.cpp b/RayTracer/tools/Transformation.cpp
index 86eed883edda090a13230766267229475e936986..d5149d877fff613c4124a9eb050aa0e2a92709ed 100644
--- a/RayTracer/tools/Transformation.cpp
+++ b/RayTracer/tools/Transformation.cpp
@@ -1,7 +1,7 @@
 #include "Transformation.h"
 
 namespace util {
-util::Transformation::Transformation(Mat4 matrix)
+util::Transformation::Transformation(const Mat4& matrix)
     : toWorld(matrix),
       fromWorld(matrix.invertFull()),
       toWorldN(matrix.invertFull().transpose()) {
diff --git a/RayTracer/tools/Transformation.h b/RayTracer/tools/Transformation.h
index 43d05b91e976d80649e560e7403fd3e5835b2ecb..f5e09a5cf2980ded501164c58f80b013ea02e423 100644
--- a/RayTracer/tools/Transformation.h
+++ b/RayTracer/tools/Transformation.h
@@ -4,7 +4,7 @@
 namespace util {
 class Transformation {
    public:
-	Transformation(Mat4 matrix);
+	Transformation(const Mat4& matrix);
 	const Mat4 toWorld, fromWorld, toWorldN;
 };
 }  // namespace util
\ No newline at end of file