diff --git a/tools/bifcl/bif_arg.cc b/tools/bifcl/bif_arg.cc
index a0196d7bf9..920846e4a8 100644
--- a/tools/bifcl/bif_arg.cc
+++ b/tools/bifcl/bif_arg.cc
@@ -1,12 +1,7 @@
-
-#include <set>
-#include <string>
-using namespace std;
-
-#include <string.h>
-
 #include "bif_arg.h"
 
+#include <cstring>
+
 static struct {
     const char* type_enum;
     const char* bif_type;
diff --git a/tools/bifcl/builtin-func.l b/tools/bifcl/builtin-func.l
index a2e73e8a46..9b4d4628e1 100644
--- a/tools/bifcl/builtin-func.l
+++ b/tools/bifcl/builtin-func.l
@@ -1,15 +1,15 @@
 %top{
-// Include stdint.h at the start of the generated file. Typically
+// Include cstdint at the start of the generated file. Typically
 // MSVC will include this header later, after the definitions of
 // the integral type macros. MSVC then complains that about the
-// redefinition of the types. Including stdint.h early avoids this.
-#include <stdint.h>
+// redefinition of the types. Including cstdint early avoids this.
+#include <cstdint>
 }
 
 %{
 #include <ctype.h>
-#include <string.h>
 #include <unistd.h>
+#include <cstring>
 #include <memory>
 #include "bif_arg.h"
 #include "bif_parse.h"
diff --git a/tools/bifcl/builtin-func.y b/tools/bifcl/builtin-func.y
index 901f7892fd..46dd4fb4fa 100644
--- a/tools/bifcl/builtin-func.y
+++ b/tools/bifcl/builtin-func.y
@@ -1,11 +1,10 @@
 %{
+#include <cstdio>
+#include <cstdlib>
+#include <cstring>
 #include <vector>
 #include <set>
 #include <string>
-#include <cstring>
-
-#include <stdio.h>
-#include <stdlib.h>
 
 #include "module_util.h"
 
diff --git a/tools/bifcl/include/bif_arg.h b/tools/bifcl/include/bif_arg.h
index f983e89dd6..7a62d34af8 100644
--- a/tools/bifcl/include/bif_arg.h
+++ b/tools/bifcl/include/bif_arg.h
@@ -1,6 +1,7 @@
 #pragma once
 
-#include <stdio.h>
+#include <cstdint>
+#include <cstdio>
 
 enum builtin_func_arg_type {
 #define DEFINE_BIF_TYPE(id, bif_type, bro_type, c_type, c_type_smart, accessor, accessor_smart, cast_smart,            \