diff --git a/ProcessLib/Assembly/MatrixOutput.cpp b/ProcessLib/Assembly/MatrixOutput.cpp
index 388b81edfa6..d5d1b872e20 100644
--- a/ProcessLib/Assembly/MatrixOutput.cpp
+++ b/ProcessLib/Assembly/MatrixOutput.cpp
@@ -12,6 +12,7 @@
 
 #include <spdlog/fmt/bundled/ostream.h>
 
+#include <iomanip>
 #include <optional>
 #include <unordered_set>