diff --git a/include/fmt/format-inl.h b/include/fmt/format-inl.h
index a231ab1d..d9e37d20 100644
--- a/include/fmt/format-inl.h
+++ b/include/fmt/format-inl.h
@@ -10,7 +10,7 @@
 
 #include "format.h"
 
-#include <string.h>
+#include <cstring>
 
 #include <cctype>
 #include <cerrno>
diff --git a/include/fmt/posix.h b/include/fmt/posix.h
index 3ed3b055..0651f047 100644
--- a/include/fmt/posix.h
+++ b/include/fmt/posix.h
@@ -13,11 +13,11 @@
 #  undef __STRICT_ANSI__
 #endif
 
-#include <errno.h>
+#include <cerrno>
 #include <fcntl.h>   // for O_RDONLY
-#include <locale.h>  // for locale_t
-#include <stdio.h>
-#include <stdlib.h>  // for strtod_l
+#include <clocale>  // for locale_t
+#include <cstdio>
+#include <cstdlib>  // for strtod_l
 
 #include <cstddef>