diff --git a/reading_machine/src/Config.cpp b/reading_machine/src/Config.cpp
index faeb04fc4277d9e659c204c7135ce9c12f0eedb9..fe65a0698d9627a758a9d754f7b1b0d303d05a77 100644
--- a/reading_machine/src/Config.cpp
+++ b/reading_machine/src/Config.cpp
@@ -393,7 +393,7 @@ bool Config::hasHistory(int relativeIndex) const
 
 bool Config::hasStack(int relativeIndex) const
 {
-  return relativeIndex > 0 && relativeIndex < (int)stack.size();
+  return relativeIndex >= 0 && relativeIndex < (int)stack.size();
 }
 
 Config::String Config::getState() const