diff --git a/poincare/src/matrix_identity.cpp b/poincare/src/matrix_identity.cpp
index c015030d8..6cadf5968 100644
--- a/poincare/src/matrix_identity.cpp
+++ b/poincare/src/matrix_identity.cpp
@@ -49,7 +49,9 @@ Expression MatrixIdentity::shallowReduce(ExpressionNode::ReductionContext reduct
     }
   }
   Expression c = childAtIndex(0);
-  if (!c.isRationalOne()) {
+  if (c.type() != ExpressionNode::Type::Rational
+      || !static_cast<Rational&>(c).isInteger())
+  {
     return replaceWithUndefinedInPlace();
   }
   Integer dimension = static_cast<Rational &>(c).signedIntegerNumerator();