diff --git a/poincare/test/helper.cpp b/poincare/test/helper.cpp
index ed48fc70f..90e0af046 100644
--- a/poincare/test/helper.cpp
+++ b/poincare/test/helper.cpp
@@ -141,7 +141,11 @@ void assert_parsed_expression_evaluates_to(const char * expression, const char *
   int numberOfDigits = sizeof(T) == sizeof(double) ? PrintFloat::k_numberOfStoredSignificantDigits : PrintFloat::k_numberOfPrintedSignificantDigits;
   numberOfDigits = numberOfSignificantDigits > 0 ? numberOfSignificantDigits : numberOfDigits;
   assert_parsed_expression_process_to(expression, approximation, angleUnit, complexFormat, [](Expression e, Context & context, Preferences::AngleUnit angleUnit, Preferences::ComplexFormat complexFormat) {
-        return e.simplify(context, angleUnit).approximate<T>(context, angleUnit, complexFormat);
+        Expression result = e.clone().simplify(context, angleUnit);
+        if (result.isUninitialized()) {
+          result = e;
+        }
+        return result.approximate<T>(context, angleUnit, complexFormat);
       }, numberOfDigits);
 }
 
@@ -149,7 +153,12 @@ void assert_parsed_expression_simplify_to(const char * expression, const char *
 #if POINCARE_TESTS_PRINT_EXPRESSIONS
   cout << "--------- Simplification ---------" << endl;
 #endif
-  assert_parsed_expression_process_to(expression, simplifiedExpression, angleUnit, Preferences::ComplexFormat::Cartesian, [](Expression e, Context & context, Preferences::AngleUnit angleUnit, Preferences::ComplexFormat complexFormat) { return e.simplify(context, angleUnit); });
+  assert_parsed_expression_process_to(expression, simplifiedExpression, angleUnit, Preferences::ComplexFormat::Cartesian, [](Expression e, Context & context, Preferences::AngleUnit angleUnit, Preferences::ComplexFormat complexFormat) {
+      Expression result = e.clone().simplify(context, angleUnit);
+      if (result.isUninitialized()) {
+        return e;
+      }
+      return result;});
 }
 
 void assert_parsed_expression_serialize_to(Expression expression, const char * serializedExpression, Preferences::PrintFloatMode mode, int numberOfSignifiantDigits) {
diff --git a/poincare/test/store.cpp b/poincare/test/store.cpp
index ba355bffc..82776f623 100644
--- a/poincare/test/store.cpp
+++ b/poincare/test/store.cpp
@@ -72,14 +72,24 @@ QUIZ_CASE(poincare_store_that_should_fail) {
 }
 
 QUIZ_CASE(poincare_store_overwrite) {
+  assert_parsed_expression_simplify_to("2>g", "2");
+  assert_parsed_expression_simplify_to("-1>g(x)", "-1");
+  assert_parsed_expression_evaluates_to<double>("g(4)", "-1");
+
+  // Clean the storage for other tests
+  Ion::Storage::sharedStorage()->recordNamed("g.func").destroy();
+}
+
+QUIZ_CASE(poincare_store_do_not_overwrite) {
   assert_parsed_expression_simplify_to("-1>g(x)", "-1");
   assert_parsed_expression_simplify_to("1+g(x)>f(x)", "1+g(?)");
-  assert_parsed_expression_simplify_to("2>g", "2");
-  assert_parsed_expression_evaluates_to<double>("g(4)", "undef");
-  assert_parsed_expression_evaluates_to<double>("f(4)", "undef");
+  assert_parsed_expression_simplify_to("2>g", "undef");
+  assert_parsed_expression_evaluates_to<double>("g(4)", "-1");
+  assert_parsed_expression_evaluates_to<double>("f(4)", "0");
+
   // Clean the storage for other tests
   Ion::Storage::sharedStorage()->recordNamed("f.func").destroy();
-  Ion::Storage::sharedStorage()->recordNamed("g.exp").destroy();
+  Ion::Storage::sharedStorage()->recordNamed("g.func").destroy();
 }
 
 QUIZ_CASE(poincare_store_2_circular_variables) {