diff --git a/poincare/include/poincare/kmat.h b/poincare/include/poincare/kmat.h
index f45873595..d0e5df23a 100644
--- a/poincare/include/poincare/kmat.h
+++ b/poincare/include/poincare/kmat.h
@@ -34,7 +34,10 @@ private:
   // Evaluation
   Evaluation<float> approximate(SinglePrecision p, ApproximationContext approximationContext) const override { return templatedApproximate<float>(approximationContext); }
   Evaluation<double> approximate(DoublePrecision p, ApproximationContext approximationContext) const override { return templatedApproximate<double>(approximationContext); }
-  template<typename T> Evaluation<T> templatedApproximate(ApproximationContext approximationContext) const;
+  template<typename T>
+  Evaluation<T> templatedApproximate(ApproximationContext approximationContext) const {
+    return Complex<T>::Undefined();
+  }
 };
 
 class KMat final : public Expression {
diff --git a/poincare/src/kmat.cpp b/poincare/src/kmat.cpp
index 9bea459f1..45a7a891c 100644
--- a/poincare/src/kmat.cpp
+++ b/poincare/src/kmat.cpp
@@ -30,11 +30,6 @@ Expression KMatNode::shallowReduce(ExpressionNode::ReductionContext reductionCon
   return KMat(this).shallowReduce(reductionContext);
 }
 
-template<typename T>
-Evaluation<T> KMatNode::templatedApproximate(ApproximationContext approximationContext) const {
-  return Complex<T>::Undefined();
-}
-
 Expression KMat::shallowReduce(ExpressionNode::ReductionContext reductionContext) {
   Expression c0 = childAtIndex(0);
   Expression c1 = childAtIndex(1);