diff --git a/ruby/ext/google/protobuf_c/protobuf.c b/ruby/ext/google/protobuf_c/protobuf.c
index 65263a44cf1..490cda670b0 100644
--- a/ruby/ext/google/protobuf_c/protobuf.c
+++ b/ruby/ext/google/protobuf_c/protobuf.c
@@ -180,6 +180,7 @@ static void Arena_mark(void *data) {
 static void Arena_free(void *data) {
   Arena *arena = data;
   upb_arena_free(arena->arena);
+  xfree(arena);
 }
 
 static VALUE cArena;