diff --git a/src/config/config.hpp b/src/config/config.hpp
index 78ec14b78..139c1f97a 100644
--- a/src/config/config.hpp
+++ b/src/config/config.hpp
@@ -37,6 +37,8 @@
 #define MPICH_SKIP_MPICXX
 #endif
 
+#include <cstddef>
+
 #include "config-features.hpp"
 
 /** P3M: Default for number of interpolation points of the charge
diff --git a/src/utils/include/utils/NumeratedContainer.hpp b/src/utils/include/utils/NumeratedContainer.hpp
index 1d99098f0..36602b203 100644
--- a/src/utils/include/utils/NumeratedContainer.hpp
+++ b/src/utils/include/utils/NumeratedContainer.hpp
@@ -25,6 +25,7 @@
  */
 
 #include <cassert>
+#include <cstddef>
 #include <set>
 #include <unordered_map>