diff --git a/src/Psalm/Internal/Analyzer/Statements/Block/LoopAnalyzer.php b/src/Psalm/Internal/Analyzer/Statements/Block/LoopAnalyzer.php
index 0ed1a446a..83033d4aa 100644
--- a/src/Psalm/Internal/Analyzer/Statements/Block/LoopAnalyzer.php
+++ b/src/Psalm/Internal/Analyzer/Statements/Block/LoopAnalyzer.php
@@ -155,6 +155,8 @@ class LoopAnalyzer
 
             $original_mixed_counts = $analyzer->getMixedCountsForFile($statements_analyzer->getFilePath());
 
+            $pre_condition_vars_in_scope = $loop_scope->loop_context->vars_in_scope;
+
             IssueBuffer::startRecording();
 
             foreach ($pre_conditions as $condition_offset => $pre_condition) {
@@ -315,6 +317,15 @@ class LoopAnalyzer
                 $analyzer->setMixedCountsForFile($statements_analyzer->getFilePath(), $original_mixed_counts);
                 IssueBuffer::startRecording();
 
+                foreach ($pre_loop_context->vars_in_scope as $var_id => $_) {
+                    if (!isset($pre_condition_vars_in_scope[$var_id])
+                        && strpos($var_id, '->') === false
+                        && strpos($var_id, '[') === false
+                    ) {
+                        $inner_context->vars_in_scope[$var_id]->possibly_undefined = true;
+                    }
+                }
+
                 foreach ($pre_conditions as $condition_offset => $pre_condition) {
                     self::applyPreConditionToLoopContext(
                         $statements_analyzer,
diff --git a/tests/Loop/WhileTest.php b/tests/Loop/WhileTest.php
index 2e54e1b31..92295b91f 100644
--- a/tests/Loop/WhileTest.php
+++ b/tests/Loop/WhileTest.php
@@ -394,7 +394,20 @@ class WhileTest extends \Psalm\Tests\TestCase
                             $i++;
                         }
                     }'
-            ]
+            ],
+            'possiblyUndefinedInWhile' => [
+                '<?php
+                    function getRenderersForClass(string $a): void {
+                        /** @psalm-suppress MixedArgument */
+                        while ($b = getString($b ?? $a)) {
+                            $c = "hello";
+                        }
+                    }
+
+                    function getString(string $s) : ?string {
+                        return rand(0, 1) ? $s : null;
+                    }'
+            ],
         ];
     }