diff --git a/poincare/src/expression_debug.h b/poincare/src/expression_debug.h
index b251b6cc3..5c28c9901 100644
--- a/poincare/src/expression_debug.h
+++ b/poincare/src/expression_debug.h
@@ -1,3 +1,8 @@
+#ifndef POICARE_EXPRESSION_DEBUG_H
+#define POICARE_EXPRESSION_DEBUG_H
+
 #include <poincare/expression.h>
 
 void print_expression(const Expression * e, int indentationLevel = 0);
+
+#endif // POICARE_EXPRESSION_DEBUG_H