diff --git a/rules-tests/DeadCode/Rector/For_/RemoveDeadIfForeachForRector/Fixture/skip_foreach_over_call_side_effect.php.inc b/rules-tests/DeadCode/Rector/For_/RemoveDeadIfForeachForRector/Fixture/skip_foreach_over_call_side_effect.php.inc
new file mode 100644
index 00000000000..fc5c907e16d
--- /dev/null
+++ b/rules-tests/DeadCode/Rector/For_/RemoveDeadIfForeachForRector/Fixture/skip_foreach_over_call_side_effect.php.inc
@@ -0,0 +1,24 @@
+<?php
+
+namespace Rector\Tests\DeadCode\Rector\For_\RemoveDeadIfForeachForRector\Fixture;
+
+class SkipForeachOverCallSideEffect
+{
+    private $result;
+
+    public function run()
+    {
+        if (! isset($this->result)) {
+            foreach ($this->events() as $event) {
+            }
+        }
+
+        return $this->result;
+    }
+
+    private function events(): iterable
+    {
+        $this->result = 1;
+        yield 1;
+    }
+}
diff --git a/rules/DeadCode/Rector/For_/RemoveDeadIfForeachForRector.php b/rules/DeadCode/Rector/For_/RemoveDeadIfForeachForRector.php
index fef1be4bb0f..f4a86bb53ba 100644
--- a/rules/DeadCode/Rector/For_/RemoveDeadIfForeachForRector.php
+++ b/rules/DeadCode/Rector/For_/RemoveDeadIfForeachForRector.php
@@ -166,6 +166,11 @@ private function processForForeach(For_|Foreach_ $for, int $key, Node $stmtsAwar
             return;
         }
 
+        // the iterated expression itself may have side effects, e.g. foreach (generator() as $event) {}
+        if ($this->hasNodeSideEffect($for->expr)) {
+            return;
+        }
+
         $exprs = [$for->expr, $for->valueVar, $for->valueVar];
         $variables = $this->betterNodeFinder->findInstanceOf($exprs, Variable::class);
         foreach ($variables as $variable) {