diff --git a/lectures/optimization/emplace_back/emplace_back_faster.cpp b/lectures/optimization/emplace_back/emplace_back_faster.cpp
index 336ea00..c00d543 100644
--- a/lectures/optimization/emplace_back/emplace_back_faster.cpp
+++ b/lectures/optimization/emplace_back/emplace_back_faster.cpp
@@ -1,6 +1,5 @@
 #include <iostream>
 #include <vector>
-#include <chrono>
 #include <cstring>
 
 class LargeObject {
diff --git a/lectures/optimization/emplace_back/emplace_back_fastest.cpp b/lectures/optimization/emplace_back/emplace_back_fastest.cpp
index 9424bc9..f6751da 100644
--- a/lectures/optimization/emplace_back/emplace_back_fastest.cpp
+++ b/lectures/optimization/emplace_back/emplace_back_fastest.cpp
@@ -1,6 +1,5 @@
 #include <iostream>
 #include <vector>
-#include <chrono>
 #include <cstring>
 
 class LargeObject {
diff --git a/lectures/optimization/emplace_back/emplace_back_slower.cpp b/lectures/optimization/emplace_back/emplace_back_slower.cpp
index f9b95e4..d3a1bd9 100644
--- a/lectures/optimization/emplace_back/emplace_back_slower.cpp
+++ b/lectures/optimization/emplace_back/emplace_back_slower.cpp
@@ -1,6 +1,5 @@
 #include <iostream>
 #include <vector>
-#include <chrono>
 #include <cstring>
 
 class LargeObject {