diff --git a/src/libslic3r/Brim.cpp b/src/libslic3r/Brim.cpp
index 0dc528819..78a6bad70 100644
--- a/src/libslic3r/Brim.cpp
+++ b/src/libslic3r/Brim.cpp
@@ -9,6 +9,7 @@
 
 #include <algorithm>
 #include <numeric>
+#include <unordered_set>
 #include <tbb/parallel_for.h>
 
 #ifndef NDEBUG