diff --git a/lib/extension/RexFunctionsDynamicReturnTypeExtension.php b/lib/extension/RexFunctionsDynamicReturnTypeExtension.php
index 19535e484..4986425a7 100644
--- a/lib/extension/RexFunctionsDynamicReturnTypeExtension.php
+++ b/lib/extension/RexFunctionsDynamicReturnTypeExtension.php
@@ -7,6 +7,7 @@
 use PhpParser\Node\Arg;
 use PhpParser\Node\Expr\FuncCall;
 use PhpParser\Node\Expr\StaticCall;
+use PhpParser\Node\Scalar\String_;
 use PHPStan\Analyser\Scope;
 use PHPStan\Reflection\FunctionReflection;
 use PHPStan\Reflection\MethodReflection;
@@ -74,14 +75,17 @@ private function getType(array $args, Scope $scope): ?Type
             return null;
         }
 
-        $defaultArgType = new ConstantStringType('');
+        $results = [];
         if (count($args) >= 3) {
             $defaultArgType = $scope->getType($args[2]->value);
+            $defaultArgTypeStrings = $defaultArgType->getConstantStrings();
+            if (count($defaultArgTypeStrings) !== 1 || $defaultArgTypeStrings[0]->getValue() !== '') {
+                $results[] = $defaultArgType;
+            }
         }
 
         $typeStrings = $scope->getType($args[1]->value)->getConstantStrings();
         if (count($typeStrings) > 0) {
-            $results = [];
             foreach ($typeStrings as $typeString) {
                 $resolvedType = $this->resolveTypeFromString($typeString->getValue());
                 if ($resolvedType === null) {
@@ -91,7 +95,7 @@ private function getType(array $args, Scope $scope): ?Type
                 $results[] = $resolvedType;
             }
 
-            return TypeCombinator::union($defaultArgType, ...$results);
+            return TypeCombinator::union(...$results);
         }
 
         return null;
diff --git a/tests/data/rex-sapi.php b/tests/data/rex-sapi.php
index 594024b8f..e77c496fc 100644
--- a/tests/data/rex-sapi.php
+++ b/tests/data/rex-sapi.php
@@ -30,11 +30,19 @@ function doBar()
 function doFooBar()
 {
     assertType('string', rex_get('HTTP_REFERER', 'string', ''));
-    assertType("''|int", rex_get('HTTP_REFERER', 'int', ''));
-    assertType("''|int", rex_get('HTTP_REFERER', 'integer', ''));
-    assertType("''|float", rex_get('HTTP_REFERER', 'float', ''));
-    assertType("''|float", rex_get('HTTP_REFERER', 'double', ''));
-    assertType("''|float", rex_get('HTTP_REFERER', 'real', ''));
-    assertType("''|bool", rex_get('HTTP_REFERER', 'bool', ''));
-    assertType("''|bool", rex_get('HTTP_REFERER', 'boolean', ''));
+    assertType('int', rex_get('HTTP_REFERER', 'int', ''));
+    assertType('int', rex_get('HTTP_REFERER', 'integer', ''));
+    assertType('float', rex_get('HTTP_REFERER', 'float', ''));
+    assertType('float', rex_get('HTTP_REFERER', 'double', ''));
+    assertType('float', rex_get('HTTP_REFERER', 'real', ''));
+    assertType('bool', rex_get('HTTP_REFERER', 'bool', ''));
+    assertType('bool', rex_get('HTTP_REFERER', 'boolean', ''));
+}
+
+function doQux()
+{
+    assertType('int', rex_get('HTTP_REFERER', 'int', 1));
+    assertType('int|null', rex_get('HTTP_REFERER', 'int', null));
+    assertType("'foo'|int", rex_get('HTTP_REFERER', 'int', 'foo'));
+    assertType("'foo'|int", rex_get('HTTP_REFERER', 'int', rand(0,1) ? 'foo' : ''));
 }