diff --git a/src/control_backend/agents/bdi/agentspeak_generator.py b/src/control_backend/agents/bdi/agentspeak_generator.py
index 9618a4a..0197d86 100644
--- a/src/control_backend/agents/bdi/agentspeak_generator.py
+++ b/src/control_backend/agents/bdi/agentspeak_generator.py
@@ -107,7 +107,7 @@ class AgentSpeakGenerator:
         check if a keyword is a substring of the user's message.
 
         The generated rule has the form:
-        keyword_said(Keyword) :- user_said(Message) & .substring(Keyword, Message, Pos) & Pos >= 0
+        keyword_said(Keyword) :- user_said(Message) & .substring_case_insensitive(Keyword, Message, Pos) & Pos >= 0
 
         This enables the system to trigger behaviors based on keyword detection.
         """
@@ -119,7 +119,7 @@ class AgentSpeakGenerator:
             AstRule(
                 AstLiteral("keyword_said", [keyword]),
                 AstLiteral("user_said", [message])
-                & AstLiteral(".substring", [keyword, message, position])
+                & AstLiteral(".substring_case_insensitive", [keyword, message, position])
                 & (position >= 0),
             )
         )
diff --git a/src/control_backend/agents/bdi/bdi_core_agent.py b/src/control_backend/agents/bdi/bdi_core_agent.py
index 05b93b8..ffad8ce 100644
--- a/src/control_backend/agents/bdi/bdi_core_agent.py
+++ b/src/control_backend/agents/bdi/bdi_core_agent.py
@@ -342,6 +342,28 @@ class BDICoreAgent(BaseAgent):
         the function expects (which will be located in `term.args`).
         """
 
+        @self.actions.add(".substring_case_insensitive", 3)
+        @agentspeak.optimizer.function_like
+        def _substring(agent, term, intention):
+            """
+            Find out if a string is a substring of another (case insensitive). Copied mostly from
+            the agentspeak library method .substring.
+            """
+            needle = agentspeak.asl_str(agentspeak.grounded(term.args[0], intention.scope)).lower()
+            haystack = agentspeak.asl_str(agentspeak.grounded(term.args[1], intention.scope)).lower()
+
+            choicepoint = object()
+
+            pos = haystack.find(needle)
+            while pos != -1:
+                intention.stack.append(choicepoint)
+
+                if agentspeak.unify(term.args[2], pos, intention.scope, intention.stack):
+                    yield
+
+                agentspeak.reroll(intention.scope, intention.stack, choicepoint)
+                pos = haystack.find(needle, pos + 1)
+
         @self.actions.add(".reply", 2)
         def _reply(agent, term, intention):
             """
@@ -467,7 +489,6 @@ class BDICoreAgent(BaseAgent):
                 body=str(trigger_name),
             )
 
-            # TODO: check with Pim
             self.add_behavior(self.send(msg))
 
             yield