diff --git a/src/Analyser/MutatingScope.php b/src/Analyser/MutatingScope.php
index 395626e1ce..e4e92d074e 100644
--- a/src/Analyser/MutatingScope.php
+++ b/src/Analyser/MutatingScope.php
@@ -4238,7 +4238,7 @@ public function specifyExpressionType(Expr $expr, Type $type, Type $nativeType,
 						new ObjectType(ArrayAccess::class),
 						new NullType(),
 					];
-					if ($dimType instanceof ConstantIntegerType) {
+					if ($dimType->isInteger()->yes()) {
 						$types[] = new StringType();
 					}