diff --git a/stub/returns.zep b/stub/returns.zep
index 702930d26..17a2ec9a5 100644
--- a/stub/returns.zep
+++ b/stub/returns.zep
@@ -3,6 +3,8 @@ namespace Stub;
 
 class Returns
 {
+    protected stringDefaultNull = null;
+
 	public function testReturnCast1() -> int
 	{
 		return (int) 5.0;
@@ -36,4 +38,12 @@ class Returns
 	{
 		return "Return back";
 	}
+
+    /**
+     * @issue https://github.com/zephir-lang/zephir/issues/1991
+     */
+	public function returnNullOnString() -> string
+	{
+	    return this->stringDefaultNull;
+	}
 }
diff --git a/tests/Extension/ReturnsTest.php b/tests/Extension/ReturnsTest.php
index 43c052d98..d2da1ed39 100644
--- a/tests/Extension/ReturnsTest.php
+++ b/tests/Extension/ReturnsTest.php
@@ -51,4 +51,16 @@ public function testShouldReturnWithoutParameterStaticVersion(): void
     {
         $this->assertSame('Return back', Returns::returnWithoutParameter());
     }
+
+    /**
+     * @issue https://github.com/zephir-lang/zephir/issues/1991
+     */
+    public function testIssue1991ShouldThrow(): void
+    {
+        $tester = new Returns();
+
+        $this->expectException(\TypeError::class);
+
+        $tester->returnNullOnString();
+    }
 }