diff --git a/poincare/src/expression.cpp b/poincare/src/expression.cpp
index 2b95ece7c..5e3652b2a 100644
--- a/poincare/src/expression.cpp
+++ b/poincare/src/expression.cpp
@@ -856,8 +856,13 @@ Expression Expression::CreateComplexExpression(Expression ra, Expression tb, Pre
       Expression norm;
       Expression exp;
       if (!isOneRa || isZeroTb) {
-        assert(!isNegativeRa); // norm cannot be negative
-        norm = ra;
+        /* Norm cannot be negative but can be preceded by a negative sign (for
+         * instance "-log(0.3)") which would lead to isNegativeRa = True. */
+        if (isNegativeRa) {
+          norm = Opposite::Builder(ra);
+        } else {
+          norm = ra;
+        }
       }
       if (!isZeroRa && !isZeroTb) {
         Expression arg;
diff --git a/poincare/test/simplification.cpp b/poincare/test/simplification.cpp
index 9379274d4..86a546098 100644
--- a/poincare/test/simplification.cpp
+++ b/poincare/test/simplification.cpp
@@ -941,6 +941,7 @@ QUIZ_CASE(poincare_simplification_complex_format) {
   assert_parsed_expression_simplify_to("[[1,√(-1)]]", "[[1,ℯ^\u0012π/2×𝐢\u0013]]", User, Radian, Polar);
   assert_parsed_expression_simplify_to("atan(2)", "atan(2)", User, Radian, Polar);
   assert_parsed_expression_simplify_to("atan(-2)", "atan(2)×ℯ^\u0012π×𝐢\u0013", User, Radian, Polar);
+  assert_parsed_expression_simplify_to("cos(42π)", "-cos(42×π)×ℯ^\x12π×𝐢\x13", User, Degree, Polar);
 
   // User defined variable
   assert_parsed_expression_simplify_to("a", "a", User, Radian, Polar);