diff --git a/nexosim/src/simulation.rs b/nexosim/src/simulation.rs
index 1a606a5..cf20b02 100644
--- a/nexosim/src/simulation.rs
+++ b/nexosim/src/simulation.rs
@@ -344,17 +344,15 @@ impl Simulation {
 
     /// Runs the executor.
     fn run(&mut self) -> Result<(), ExecutionError> {
-        // Defensive programming, shouldn't happen
-        if !self.is_terminated && self.is_halted.load(Ordering::Relaxed) {
-            self.is_terminated = true;
-            return Err(ExecutionError::Halted);
-        }
-
-        // Defensive programming, shouldn't happen
         if self.is_terminated {
             return Err(ExecutionError::Terminated);
         }
 
+        if self.is_halted.load(Ordering::Relaxed) {
+            self.is_terminated = true;
+            return Err(ExecutionError::Halted);
+        }
+
         self.executor.run(self.timeout).map_err(|e| {
             self.is_terminated = true;
 
@@ -409,15 +407,15 @@ impl Simulation {
         &mut self,
         upper_time_bound: Option<MonotonicTime>,
     ) -> Result<Option<MonotonicTime>, ExecutionError> {
-        if !self.is_terminated && self.is_halted.load(Ordering::Relaxed) {
-            self.is_terminated = true;
-            return Err(ExecutionError::Halted);
-        }
-
         if self.is_terminated {
             return Err(ExecutionError::Terminated);
         }
 
+        if self.is_halted.load(Ordering::Relaxed) {
+            self.is_terminated = true;
+            return Err(ExecutionError::Halted);
+        }
+
         // Function pulling the next action. If the action is periodic, it is
         // immediately re-scheduled.
         fn pull_next_action(scheduler_queue: &mut MutexGuard<SchedulerQueue>) -> Action {