diff --git a/src/c/stacks.d b/src/c/stacks.d
index e74e7efbd..ce3e74a03 100644
--- a/src/c/stacks.d
+++ b/src/c/stacks.d
@@ -274,7 +274,7 @@ ecl_new_binding_index(cl_env_ptr env, cl_object symbol)
     symbol->symbol.binding = new_index;
     symbol->symbol.dynamic |= 1;
   }
-  si_set_finalizer(symbol, ECL_T);
+  ecl_set_finalizer_unprotected(symbol, ECL_T);
   return new_index;
 }
 
diff --git a/src/tests/ecl-tests.lisp b/src/tests/ecl-tests.lisp
index cf6835517..97223ff82 100644
--- a/src/tests/ecl-tests.lisp
+++ b/src/tests/ecl-tests.lisp
@@ -29,39 +29,21 @@
          ffi mop run-program))
 
 
-;;; Some syntactic sugar for 2am
-(defmacro once-only (specs &body body)
-  "Once-Only ({(Var Value-Expression)}*) Form*
-
-  Create a Let* which evaluates each Value-Expression, binding a
-  temporary variable to the result, and wrapping the Let* around the
-  result of the evaluation of Body.  Within the body, each Var is
-  bound to the corresponding temporary variable."
-  (labels ((frob (specs body)
-             (if (null specs)
-                 `(progn ,@body)
-                 (let ((spec (first specs)))
-                   (when (/= (length spec) 2)
-                     (error "Malformed Once-Only binding spec: ~S." spec))
-                   (let ((name (first spec))
-                         (exp-temp (gensym)))
-                     `(let ((,exp-temp ,(second spec))
-                            (,name (gensym "OO-")))
-                        `(let ((,,name ,,exp-temp))
-                           ,,(frob (rest specs) body))))))))
-    (frob specs body)))
-
 (defmacro is-true (form)
-  `(is (eql ,form t) "Expected T, but got ~s" ,form))
+  (ext:once-only (form)
+    `(is (eql ,form t) "Expected T, but got ~s" ,form)))
 
 (defmacro is-false (form)
-  `(is (null ,form) "Expected NIL, but got ~s" ,form))
+  (ext:once-only (form)
+    `(is (null ,form) "Expected NIL, but got ~s" ,form)))
 
 (defmacro is-equal (what form)
-  `(is (equal ,what ,form) "EQUAL: ~s to ~s" ,form ,what))
+  (ext:once-only (what form)
+    `(is (equal ,what ,form) "EQUAL: ~s to ~s" ,what ,form)))
 
 (defmacro is-eql (what form)
-  `(is (eql ,what ,form) "EQL: ~s to ~s" ,what ,form))
+  (ext:once-only (what form)
+    `(is (eql ,what ,form) "EQL: ~s to ~a" ,what ,form)))
 
 (defmacro pass (form &rest args)
   (declare (ignore form args))
@@ -119,6 +101,10 @@ as a second value."
                      (*compile-verbose* t)
                      (*compile-print* t))
                  (setf compiled-file (compile-file ,filename ,@compiler-args))))))
+       ;; todo: add delete-files flag
+       ;; (when delete-files
+       ;;   (delete-file filename)
+       ;;   (delete-file compiled-file))
        (values compiled-file output))))
 
 (defmacro with-temporary-file ((var string &rest args) &body body)
diff --git a/src/tests/normal-tests/mixed.lsp b/src/tests/normal-tests/mixed.lsp
index f2ddf9a73..18e49f770 100644
--- a/src/tests/normal-tests/mixed.lsp
+++ b/src/tests/normal-tests/mixed.lsp
@@ -225,3 +225,29 @@
                     (go :next)
                     (print 'skip)
                     :next))))
+
+
+;;; Data: 2017-07-02
+;;; Description:
+;;;
+;;;   Function `ecl_new_binding_index' called `si_set_finalizer',
+;;;   which resetted `env->nvalues' leading to invalid binding in mvb
+;;;   during the first function run.
+;;;
+;;; Bug: https://gitlab.com/embeddable-common-lisp/ecl/issues/233
+(test mix.0015.mvb
+  (with-compiler ("aux-cl-0003.lsp" :load t)
+    `(progn
+       (defvar mix.0015.v1 'booya)
+       (defun mix.0015.fun ()
+         (let ((share_t))
+           (multiple-value-bind (mix.0015.v1 woops)
+               (case share_t
+                 ((nil)
+                  (values 1 2)))
+             woops)))))
+  (ignore-errors
+    (delete-file "aux-cl-0003.lsp")
+    (delete-file "aux-cl-0003.fas")
+    (delete-file "aux-cl-0003.fasc"))
+  (is-eql 2 (mix.0015.fun)))