diff --git a/tools/amalgamate.py b/tools/amalgamate.py
index 9ad028636d..9640201a16 100755
--- a/tools/amalgamate.py
+++ b/tools/amalgamate.py
@@ -16,11 +16,11 @@ class Amalgamator:
     self.output_h = open(output_path + "upb.h", "w")
     self.output_c = open(output_path + "upb.c", "w")
 
-    self.output_c.write("// Amalgamated source file\n")
+    self.output_c.write("/* Amalgamated source file */\n")
     self.output_c.write('#include "upb.h"\n')
     self.output_c.write(open("upb/port_def.inc").read())
 
-    self.output_h.write("// Amalgamated source file\n")
+    self.output_h.write("/* Amalgamated source file */\n")
     self.output_h.write(open("upb/port_def.inc").read())
 
   def finish(self):
diff --git a/upb/handlers-inl.h b/upb/handlers-inl.h
index 5677a4a004..40a0047c13 100644
--- a/upb/handlers-inl.h
+++ b/upb/handlers-inl.h
@@ -7,6 +7,8 @@
 #define UPB_HANDLERS_INL_H_
 
 #include <limits.h>
+#include <stddef.h>
+#include "upb/handlers.h"
 
 #ifdef __cplusplus
 
@@ -162,8 +164,8 @@ struct FuncInfo {
  * These functions are not bound to a handler data so have no data or cleanup
  * handler. */
 struct UnboundFunc {
-  CleanupFunc *GetCleanup() { return NULL; }
-  void *GetData() { return NULL; }
+  CleanupFunc *GetCleanup() { return nullptr; }
+  void *GetData() { return nullptr; }
 };
 
 template <class R, class P1, R F(P1), class I>