diff --git a/Zend/tests/fibers/gh20483.phpt b/Zend/tests/fibers/gh20483.phpt
new file mode 100644
index 0000000000000..e06cf87258ea1
--- /dev/null
+++ b/Zend/tests/fibers/gh20483.phpt
@@ -0,0 +1,16 @@
+--TEST--
+GH-20483 (ASAN stack overflow with small fiber.stack_size INI value)
+--INI--
+fiber.stack_size=1024
+--FILE--
+<?php
+$callback = function () {};
+$fiber = new Fiber($callback);
+try {
+    $fiber->start();
+} catch (Exception $e) {
+    echo $e->getMessage() . "\n";
+}
+?>
+--EXPECTF--
+Fiber stack size is too small, it needs to be at least %d bytes
diff --git a/Zend/zend_fibers.c b/Zend/zend_fibers.c
index 97b7cdcc911b7..d571a622e476b 100644
--- a/Zend/zend_fibers.c
+++ b/Zend/zend_fibers.c
@@ -207,7 +207,12 @@ static zend_fiber_stack *zend_fiber_stack_allocate(size_t size)
 {
 	void *pointer;
 	const size_t page_size = zend_fiber_get_page_size();
-	const size_t minimum_stack_size = page_size + ZEND_FIBER_GUARD_PAGES * page_size;
+	const size_t minimum_stack_size = page_size + ZEND_FIBER_GUARD_PAGES * page_size
+#ifdef __SANITIZE_ADDRESS__
+	// necessary correction due to ASAN redzones
+	* 6
+#endif
+	;
 
 	if (size < minimum_stack_size) {
 		zend_throw_exception_ex(NULL, 0, "Fiber stack size is too small, it needs to be at least %zu bytes", minimum_stack_size);