diff --git a/src/surface/mesh_ray_tracer.cpp b/src/surface/mesh_ray_tracer.cpp
index 6e6a9be0..72ec6a64 100644
--- a/src/surface/mesh_ray_tracer.cpp
+++ b/src/surface/mesh_ray_tracer.cpp
@@ -1,6 +1,22 @@
 #include "geometrycentral/surface/mesh_ray_tracer.h"
 
+// we need to include these for nanort before it tries to include them inside the anonymous namespace.
+#include <algorithm>
+#include <cassert>
+#include <cmath>
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
+#include <functional>
+#include <limits>
+#include <memory>
+#include <queue>
+#include <string>
+#include <vector>
+namespace {
+// put it in an anonymous namespace to avoid exposing symbols
 #include "nanort.h"
+} // namespace
 
 namespace geometrycentral {
 namespace surface {
diff --git a/src/utilities/knn.cpp b/src/utilities/knn.cpp
index 2bcf57a3..d9ed12a6 100644
--- a/src/utilities/knn.cpp
+++ b/src/utilities/knn.cpp
@@ -1,6 +1,26 @@
 #include "geometrycentral/utilities/knn.h"
 
+// we need to include these for nanoflann before it tries to include them inside the anonymous namespace.
+#include <algorithm>
+#include <array>
+#include <atomic>
+#include <cassert>
+#include <cmath>  // for abs()
+#include <cstdint>
+#include <cstdlib>  // for abs()
+#include <functional>  // std::reference_wrapper
+#include <future>
+#include <istream>
+#include <limits>  // std::numeric_limits
+#include <ostream>
+#include <stack>
+#include <stdexcept>
+#include <unordered_set>
+#include <vector>
+namespace {
+// put it in an anonymous namespace to avoid exposing symbols
 #include "nanoflann.hpp"
+}
 
 using std::vector;