diff --git a/upb/pb/encoder.c b/upb/pb/encoder.c
index 3734710059..839ede0cb1 100644
--- a/upb/pb/encoder.c
+++ b/upb/pb/encoder.c
@@ -374,7 +374,8 @@ static void *encode_startdelimfield(void *c, const void *hd) {
   return ok ? c : UPB_BREAK;
 }
 
-bool encode_unknown(void *c, const void *hd, const char *buf, size_t len) {
+static bool encode_unknown(void *c, const void *hd, const char *buf,
+                           size_t len) {
   UPB_UNUSED(hd);
   return encode_bytes(c, buf, len) && commit(c);
 }
diff --git a/upb/pb/encoder.h b/upb/pb/encoder.h
index 780dfcb11b..41b7e7b8db 100644
--- a/upb/pb/encoder.h
+++ b/upb/pb/encoder.h
@@ -64,8 +64,6 @@ const upb_handlers *upb_pb_encoder_newhandlers(const upb_msgdef *m,
 upb_sink *upb_pb_encoder_input(upb_pb_encoder *p);
 upb_pb_encoder* upb_pb_encoder_create(upb_env* e, const upb_handlers* h,
                                       upb_bytessink* output);
-bool encode_unknown(upb_pb_encoder* p, const void* hd, const char* buf,
-                    size_t size);
 
 UPB_END_EXTERN_C