diff --git a/CHANGELOG.md b/CHANGELOG.md
index 88a2fc4..36f253d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -31,6 +31,7 @@ process.
 - Fixed clippy warnings
 - [breaking] Changed guard functions return type from Result<(),_> to Result<bool,_>
 - [breaking] Changed action functions return type from () to Result<NextStateData,_>
+- [breaking] Disallow guards mutable access to the context
 
 ## [v0.6.0] - 2022-11-02
 
diff --git a/examples/async.rs b/examples/async.rs
index e13bbe0..b8f2816 100644
--- a/examples/async.rs
+++ b/examples/async.rs
@@ -22,19 +22,19 @@ pub struct Context {
 
 #[async_trait]
 impl StateMachineContext for Context {
-    fn guard3(&mut self) -> Result<bool, ()> {
+    fn guard3(&self) -> Result<bool, ()> {
         println!("`guard3` called from async context");
         Ok(true)
     }
 
-    async fn guard2(&mut self) -> Result<bool, ()> {
+    async fn guard2(&self) -> Result<bool, ()> {
         println!("`guard2` called from async context");
         let mut lock = self.lock.write().await;
         *lock = false;
         Ok(true)
     }
 
-    fn guard1(&mut self) -> Result<bool, ()> {
+    fn guard1(&self) -> Result<bool, ()> {
         println!("`guard1` called from sync context");
         Ok(true)
     }
diff --git a/examples/event_with_data.rs b/examples/event_with_data.rs
index ea50a92..367543b 100644
--- a/examples/event_with_data.rs
+++ b/examples/event_with_data.rs
@@ -21,7 +21,7 @@ statemachine! {
 pub struct Context;
 
 impl StateMachineContext for Context {
-    fn guard(&mut self, event_data: &MyEventData) -> Result<bool, ()> {
+    fn guard(&self, event_data: &MyEventData) -> Result<bool, ()> {
         Ok(event_data == &MyEventData(42))
     }
 
diff --git a/examples/event_with_mutable_data.rs b/examples/event_with_mutable_data.rs
index c2c8368..2f9ec92 100644
--- a/examples/event_with_mutable_data.rs
+++ b/examples/event_with_mutable_data.rs
@@ -21,7 +21,7 @@ statemachine! {
 pub struct Context;
 
 impl StateMachineContext for Context {
-    fn guard(&mut self, event_data: &mut MyEventData) -> Result<bool, ()> {
+    fn guard(&self, event_data: &mut MyEventData) -> Result<bool, ()> {
         event_data.0 = 55;
         Ok(true)
     }
diff --git a/examples/event_with_reference_data.rs b/examples/event_with_reference_data.rs
index 8e69480..c2e0791 100644
--- a/examples/event_with_reference_data.rs
+++ b/examples/event_with_reference_data.rs
@@ -21,7 +21,7 @@ statemachine! {
 pub struct Context;
 
 impl StateMachineContext for Context {
-    fn guard1(&mut self, event_data: &[u8]) -> Result<bool, ()> {
+    fn guard1(&self, event_data: &[u8]) -> Result<bool, ()> {
         // Only ok if the slice is not empty
         Ok(!event_data.is_empty())
     }
@@ -31,7 +31,7 @@ impl StateMachineContext for Context {
         Ok(())
     }
 
-    fn guard2(&mut self, event_data: &MyReferenceWrapper) -> Result<bool, ()> {
+    fn guard2(&self, event_data: &MyReferenceWrapper) -> Result<bool, ()> {
         Ok(*event_data.0 > 9000)
     }
 
diff --git a/examples/ex3.rs b/examples/ex3.rs
index 10c3a36..cfb3143 100644
--- a/examples/ex3.rs
+++ b/examples/ex3.rs
@@ -18,12 +18,12 @@ statemachine! {
 pub struct Context;
 
 impl StateMachineContext for Context {
-    fn guard(&mut self) -> Result<bool, ()> {
+    fn guard(&self) -> Result<bool, ()> {
         // Always ok
         Ok(true)
     }
 
-    fn guard_fail(&mut self) -> Result<bool, ()> {
+    fn guard_fail(&self) -> Result<bool, ()> {
         // Always fail
         Ok(false)
     }
diff --git a/examples/guard_action_syntax.rs b/examples/guard_action_syntax.rs
index 77d43e0..0fc4491 100644
--- a/examples/guard_action_syntax.rs
+++ b/examples/guard_action_syntax.rs
@@ -27,7 +27,7 @@ pub struct Context;
 
 impl StateMachineContext for Context {
     // Guard1 has access to the data from Event1
-    fn guard1(&mut self, _event_data: &MyEventData) -> Result<bool, ()> {
+    fn guard1(&self, _event_data: &MyEventData) -> Result<bool, ()> {
         todo!()
     }
 
@@ -37,7 +37,7 @@ impl StateMachineContext for Context {
     }
 
     // Guard2 has access to the data from State2
-    fn guard2(&mut self, _state_data: &MyStateData) -> Result<bool, ()> {
+    fn guard2(&self, _state_data: &MyStateData) -> Result<bool, ()> {
         todo!()
     }
 
diff --git a/examples/guard_action_syntax_with_temporary_context.rs b/examples/guard_action_syntax_with_temporary_context.rs
index a062575..4f8b2de 100644
--- a/examples/guard_action_syntax_with_temporary_context.rs
+++ b/examples/guard_action_syntax_with_temporary_context.rs
@@ -28,7 +28,7 @@ pub struct Context;
 
 impl StateMachineContext for Context {
     // Guard1 has access to the data from Event1
-    fn guard1(&mut self, temp_context: &mut u16, _event_data: &MyEventData) -> Result<bool, ()> {
+    fn guard1(&self, temp_context: &mut u16, _event_data: &MyEventData) -> Result<bool, ()> {
         *temp_context += 1;
 
         Ok(true)
@@ -46,7 +46,7 @@ impl StateMachineContext for Context {
     }
 
     // Guard2 has access to the data from State2
-    fn guard2(&mut self, temp_context: &mut u16, _state_data: &MyStateData) -> Result<bool, ()> {
+    fn guard2(&self, temp_context: &mut u16, _state_data: &MyStateData) -> Result<bool, ()> {
         *temp_context += 1;
 
         Ok(true)
diff --git a/examples/guard_custom_error.rs b/examples/guard_custom_error.rs
index e6f9839..e2d71d8 100644
--- a/examples/guard_custom_error.rs
+++ b/examples/guard_custom_error.rs
@@ -35,7 +35,7 @@ pub struct Context;
 
 impl StateMachineContext for Context {
     type GuardError = GuardError; // Guard1 has access to the data from Event1
-    fn guard1(&mut self, _event_data: &MyEventData) -> Result<bool, GuardError> {
+    fn guard1(&self, _event_data: &MyEventData) -> Result<bool, GuardError> {
         Err(GuardError::Custom)
     }
 
@@ -45,7 +45,7 @@ impl StateMachineContext for Context {
     }
 
     // Guard2 has access to the data from State2
-    fn guard2(&mut self, _state_data: &MyStateData) -> Result<bool, GuardError> {
+    fn guard2(&self, _state_data: &MyStateData) -> Result<bool, GuardError> {
         todo!()
     }
 
diff --git a/examples/named_async.rs b/examples/named_async.rs
index ac03063..ea939c2 100644
--- a/examples/named_async.rs
+++ b/examples/named_async.rs
@@ -23,12 +23,12 @@ pub struct Context {
 
 #[async_trait]
 impl AsyncSimpleStateMachineContext for Context {
-    fn guard1(&mut self) -> Result<bool, ()> {
+    fn guard1(&self) -> Result<bool, ()> {
         println!("`guard1` called from sync context");
         Ok(true)
     }
 
-    async fn guard2(&mut self) -> Result<bool, ()> {
+    async fn guard2(&self) -> Result<bool, ()> {
         println!("`guard2` called from async context");
         let mut lock = self.lock.write().await;
         *lock = false;
diff --git a/examples/named_ex3.rs b/examples/named_ex3.rs
index 062ce30..cac36b4 100644
--- a/examples/named_ex3.rs
+++ b/examples/named_ex3.rs
@@ -19,12 +19,12 @@ statemachine! {
 pub struct Context;
 
 impl LoopingWithGuardsStateMachineContext for Context {
-    fn guard(&mut self) -> Result<bool, ()> {
+    fn guard(&self) -> Result<bool, ()> {
         // Always ok
         Ok(true)
     }
 
-    fn guard_fail(&mut self) -> Result<bool, ()> {
+    fn guard_fail(&self) -> Result<bool, ()> {
         // Always fail
         Ok(false)
     }
diff --git a/examples/state_machine_logger.rs b/examples/state_machine_logger.rs
index 09a5d7c..5fea6da 100644
--- a/examples/state_machine_logger.rs
+++ b/examples/state_machine_logger.rs
@@ -30,7 +30,7 @@ pub struct Context;
 
 impl StateMachineContext for Context {
     // Guard1 has access to the data from Event1
-    fn guard1(&mut self, event_data: &MyEventData) -> Result<bool, ()> {
+    fn guard1(&self, event_data: &MyEventData) -> Result<bool, ()> {
         Ok(event_data.0 % 2 == 0)
     }
 
@@ -41,7 +41,7 @@ impl StateMachineContext for Context {
     }
 
     // Guard2 has access to the data from State2
-    fn guard2(&mut self, state_data: &MyStateData) -> Result<bool, ()> {
+    fn guard2(&self, state_data: &MyStateData) -> Result<bool, ()> {
         Ok(state_data.0 % 2 == 0)
     }
 
diff --git a/macros/src/codegen.rs b/macros/src/codegen.rs
index affd452..dd8e686 100644
--- a/macros/src/codegen.rs
+++ b/macros/src/codegen.rs
@@ -327,7 +327,7 @@ pub fn generate_code(sm: &ParsedStateMachine) -> proc_macro2::TokenStream {
                             guard_list.extend(quote! {
                             #[allow(missing_docs)]
                             #[allow(clippy::result_unit_err)]
-                            #is_async fn #guard <#all_lifetimes> (&mut self, #temporary_context #state_data #event_data) -> Result<bool,#guard_error>;
+                            #is_async fn #guard <#all_lifetimes> (&self, #temporary_context #state_data #event_data) -> Result<bool,#guard_error>;
                         });
                         };
                         Ok(())
diff --git a/tests/test.rs b/tests/test.rs
index 65a1c48..df81a33 100644
--- a/tests/test.rs
+++ b/tests/test.rs
@@ -48,15 +48,15 @@ fn multiple_lifetimes() {
     struct Context;
 
     impl StateMachineContext for Context {
-        fn guard1(&mut self, _event_data: &X) -> Result<bool, ()> {
+        fn guard1(&self, _event_data: &X) -> Result<bool, ()> {
             Ok(true)
         }
 
-        fn guard2(&mut self, _state_data: &X, _event_data: &Y) -> Result<bool, ()> {
+        fn guard2(&self, _state_data: &X, _event_data: &Y) -> Result<bool, ()> {
             Ok(true)
         }
 
-        fn guard3(&mut self, _event_data: &Z) -> Result<bool, ()> {
+        fn guard3(&self, _event_data: &Z) -> Result<bool, ()> {
             Ok(true)
         }
 
@@ -146,7 +146,7 @@ fn async_guards_and_actions() {
         struct Context;
         #[smlang::async_trait]
         impl StateMachineContext for Context {
-            async fn guard1(&mut self) -> Result<bool, ()> {
+            async fn guard1(&self) -> Result<bool, ()> {
                 Ok(true)
             }
 
@@ -186,10 +186,10 @@ fn guard_expressions() {
         attempts: u32,
     }
     impl StateMachineContext for Context {
-        fn valid_entry(&mut self, e: &Entry) -> Result<bool, ()> {
+        fn valid_entry(&self, e: &Entry) -> Result<bool, ()> {
             Ok(e.0 == self.password)
         }
-        fn too_many_attempts(&mut self, _e: &Entry) -> Result<bool, ()> {
+        fn too_many_attempts(&self, _e: &Entry) -> Result<bool, ()> {
             Ok(self.attempts >= 3)
         }
         fn reset(&mut self) -> Result<(), ()> {
@@ -260,7 +260,7 @@ fn guarded_transition_before_unguarded() {
         pub enabled: bool,
     }
     impl StateMachineContext for Context {
-        fn guard(&mut self) -> Result<bool, ()> {
+        fn guard(&self) -> Result<bool, ()> {
             Ok(self.enabled)
         }
 
@@ -294,7 +294,7 @@ fn guard_errors() {
         pub guard_errors: bool,
     }
     impl StateMachineContext for Context {
-        fn guard(&mut self) -> Result<bool, ()> {
+        fn guard(&self) -> Result<bool, ()> {
             if self.guard_errors {
                 Err(())
             } else {