diff --git a/src/vm.h b/src/vm.h
index 6acf383a..e63129cc 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -94,6 +94,7 @@ public:
         this->vm = this;
         this->_stdout = use_stdio ? &std::cout : &_stdout_buffer;
         this->_stderr = use_stdio ? &std::cerr : &_stderr_buffer;
+        callstack.data().reserve(8);
         init_builtin_types();
     }