foo.diff

diff --git a/src/Phan/Analysis/PostOrderAnalysisVisitor.php b/src/Phan/Analysis/PostOrderAnalysisVisitor.php
index a7557675d..14a631059 100644
--- a/src/Phan/Analysis/PostOrderAnalysisVisitor.php
+++ b/src/Phan/Analysis/PostOrderAnalysisVisitor.php
@@ -1632,6 +1632,7 @@ class PostOrderAnalysisVisitor extends AnalysisVisitor
         foreach ($this->getReturnTypes($context, $expr, $node->lineno) as $lineno => [$expression_type, $inner_node]) {
             // If there is no declared type, see if we can deduce
             // what it should be based on the return type
+            // TODO: this check could be performed outside the for loop? more efficient.
             if ($method_return_type->isEmpty()
                 || $method->isReturnTypeUndefined()
             ) {
@@ -1664,7 +1665,7 @@ class PostOrderAnalysisVisitor extends AnalysisVisitor
             // For functions that aren't syntactically Generators,
             // update the set/existence of return values.
 
-            if ($method->isReturnTypeModifiable() && !$is_mismatch) {
+            if ((!$method->hasDependentReturnType() || $method->isReturnTypeModifiable()) && !$is_mismatch) {
                 // Add the new type to the set of values returned by the
                 // method
                 $method->setUnionType($method->getUnionType()->withUnionType($expression_type));