diff --git a/include/ruby/internal/intern/proc.h b/include/ruby/internal/intern/proc.h
index d6f77cbd4d..003e6a0442 100644
--- a/include/ruby/internal/intern/proc.h
+++ b/include/ruby/internal/intern/proc.h
@@ -50,4 +50,6 @@ VALUE rb_protect(VALUE (*)(VALUE), VALUE, int*);
 
 RBIMPL_SYMBOL_EXPORT_END()
 
+VALUE rb_callable_receiver(VALUE);
+
 #endif /* RBIMPL_INTERN_PROC_H */