diff --git a/bindings/ruby/ext/ruby_whisper_context.c b/bindings/ruby/ext/ruby_whisper_context.c
index 8f1cacdd..eb1c102a 100644
--- a/bindings/ruby/ext/ruby_whisper_context.c
+++ b/bindings/ruby/ext/ruby_whisper_context.c
@@ -74,7 +74,7 @@ static size_t
 ruby_whisper_memsize(const void *p)
 {
   const ruby_whisper *rw = (const ruby_whisper *)p;
-  size_t size = sizeof(rw);
+  size_t size = sizeof(*rw);
   if (!rw) {
     return 0;
   }