diff --git a/phpunit/src/SsaAnalysisTest.php b/phpunit/src/SsaAnalysisTest.php
index 8ce937dc..3f7e2e82 100644
--- a/phpunit/src/SsaAnalysisTest.php
+++ b/phpunit/src/SsaAnalysisTest.php
@@ -1241,6 +1241,43 @@ class SsaAnalysisTest extends TestCase
         $this->assertArrayNotHasKey('n', $locals);
     }
 
+    public function testLoopVarOptimizerRejectsCounterReusedAsForeachKey(): void
+    {
+        $locals = $this->optimizeLoopVarsForCode('
+            foreach (["name" => 1] as $i => $value) {
+                echo $value;
+            }
+            for ($i = 0; $i < 10; $i++) {
+                echo $i;
+            }
+        ');
+
+        $this->assertArrayNotHasKey('i', $locals);
+    }
+
+    public function testLoopVarOptimizerRejectsCounterReusedAsForeachValueOrDestructuringTarget(): void
+    {
+        $valueLocals = $this->optimizeLoopVarsForCode('
+            foreach (["value"] as $i) {
+                echo $i;
+            }
+            for ($i = 0; $i < 10; $i++) {
+                echo $i;
+            }
+        ');
+        $listLocals = $this->optimizeLoopVarsForCode('
+            foreach ([["value"]] as [$i]) {
+                echo $i;
+            }
+            for ($i = 0; $i < 10; $i++) {
+                echo $i;
+            }
+        ');
+
+        $this->assertArrayNotHasKey('i', $valueLocals);
+        $this->assertArrayNotHasKey('i', $listLocals);
+    }
+
     // ========================================================================
     // SsaTypeOptimizer: detectSsaDefType
     // ========================================================================
diff --git a/src/Optimizer/LoopVarOptimizer.php b/src/Optimizer/LoopVarOptimizer.php
index 601d4a39..b0b1349c 100644
--- a/src/Optimizer/LoopVarOptimizer.php
+++ b/src/Optimizer/LoopVarOptimizer.php
@@ -758,6 +758,17 @@ trait LoopVarOptimizer
             }
         }
 
+        if ($expr instanceof Stmt\Foreach_) {
+            // Foreach key/value variables are assigned implicitly on every
+            // iteration. A name that is also used by a range-proven `for`
+            // counter cannot share a function-scoped php::Int slot with an
+            // arbitrary key or value (including list destructuring targets).
+            if (($expr->keyVar instanceof Node && $this->exprUsesVar($expr->keyVar, $varName))
+                || $this->exprUsesVar($expr->valueVar, $varName)) {
+                return true;
+            }
+        }
+
         foreach ($expr->getSubNodeNames() as $name) {
             $value = $expr->$name;
             if ($value instanceof Node) {
diff --git a/tests/compiler/optimizations/loop-counter-reused-by-foreach.phpt b/tests/compiler/optimizations/loop-counter-reused-by-foreach.phpt
new file mode 100644
index 00000000..7af0ff9e
--- /dev/null
+++ b/tests/compiler/optimizations/loop-counter-reused-by-foreach.phpt
@@ -0,0 +1,43 @@
+--TEST--
+Loop counter narrowing rejects variables previously assigned by foreach
+--FILE--
+<?php
+
+function main(): void
+{
+    foreach (['name' => 10, 20 => 30] as $i => $value) {
+        var_dump($i, $value);
+    }
+
+    for ($i = 0; $i < 2; $i++) {
+        var_dump($i);
+    }
+
+    foreach (['text'] as $i) {
+        var_dump($i);
+    }
+
+    for ($i = 0; $i < 1; $i++) {
+        var_dump($i);
+    }
+
+    foreach ([['nested']] as [$i]) {
+        var_dump($i);
+    }
+
+    for ($i = 0; $i < 1; $i++) {
+        var_dump($i);
+    }
+}
+?>
+--EXPECT--
+string(4) "name"
+int(10)
+int(20)
+int(30)
+int(0)
+int(1)
+string(4) "text"
+int(0)
+string(6) "nested"
+int(0)