diff --git a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
index b3b99faee..2f23336ac 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Expression/Fetch/ArrayFetchAnalyzer.php
@@ -646,7 +646,7 @@ class ArrayFetchAnalyzer
                 } elseif ($type instanceof TLiteralString) {
                     $valid_offsets = [];
 
-                    for ($i = 0, $l = strlen($type->value); $i < $l; $i++) {
+                    for ($i = -strlen($type->value), $l = strlen($type->value); $i < $l; $i++) {
                         $valid_offsets[] = new TLiteralInt($i);
                     }
 
diff --git a/tests/ArrayAccessTest.php b/tests/ArrayAccessTest.php
index c58129df2..43243b346 100644
--- a/tests/ArrayAccessTest.php
+++ b/tests/ArrayAccessTest.php
@@ -319,6 +319,20 @@ class ArrayAccessTest extends TestCase
                 'assertions' => [],
                 'error_levels' => ['MixedTypeCoercion'],
             ],
+            'allowNegativeStringOffset' =>  [
+                '<?php
+                    $a = "hello";
+                    echo $a[-5];
+                    echo $a[-4];
+                    echo $a[-3];
+                    echo $a[-2];
+                    echo $a[-1];
+                    echo $a[0];
+                    echo $a[1];
+                    echo $a[2];
+                    echo $a[3];
+                    echo $a[4];',
+            ],
         ];
     }
 
@@ -531,6 +545,12 @@ class ArrayAccessTest extends TestCase
                     }',
                 'error_message' => 'TypeDoesNotContainType',
             ],
+            'forbidNegativeStringOffsetOutOfRange' =>  [
+                '<?php
+                    $a = "hello";
+                    echo $a[-6];',
+                'error_message' => 'InvalidArrayOffset',
+            ],
         ];
     }
 }