diff --git a/curl/src/client.cc b/curl/src/client.cc
index 558db6d..d27bb36 100644
--- a/curl/src/client.cc
+++ b/curl/src/client.cc
@@ -1,3 +1,4 @@
+#include <cstddef>
 #include <leatherman/curl/client.hpp>
 #include <leatherman/curl/request.hpp>
 #include <leatherman/curl/response.hpp>
diff --git a/util/src/posix/scoped_descriptor.cc b/util/src/posix/scoped_descriptor.cc
index 6fd1495..8294d0b 100644
--- a/util/src/posix/scoped_descriptor.cc
+++ b/util/src/posix/scoped_descriptor.cc
@@ -1,3 +1,5 @@
+#include <cstddef>
+
 #include <leatherman/util/posix/scoped_descriptor.hpp>
 
 using namespace std;
diff --git a/util/src/scope_exit.cc b/util/src/scope_exit.cc
index 764c2fb..441855a 100644
--- a/util/src/scope_exit.cc
+++ b/util/src/scope_exit.cc
@@ -1,3 +1,4 @@
+#include <cstddef>
 #include <leatherman/util/scope_exit.hpp>
 
 using namespace std;
diff --git a/util/src/scoped_env.cc b/util/src/scoped_env.cc
index 6c6a041..df26645 100644
--- a/util/src/scoped_env.cc
+++ b/util/src/scoped_env.cc
@@ -1,3 +1,5 @@
+#include <cstddef>
+
 #include <leatherman/util/scoped_env.hpp>
 #include <leatherman/util/environment.hpp>