diff --git a/ext/zend_test/observer.c b/ext/zend_test/observer.c
index 9d0fb27c8a559..bff1d6ff93424 100644
--- a/ext/zend_test/observer.c
+++ b/ext/zend_test/observer.c
@@ -155,7 +155,7 @@ static void observer_show_init(zend_function *fbc)
 			php_printf("%*s\n", 2 * ZT_G(observer_nesting_depth), "", ZSTR_VAL(fbc->common.function_name));
 		}
 	} else {
-		php_printf("%*s\n", 2 * ZT_G(observer_nesting_depth), "", ZSTR_VAL(fbc->op_array.filename));
+		php_printf("%*s\n", 2 * ZT_G(observer_nesting_depth), "", fbc->op_array.filename ? ZSTR_VAL(fbc->op_array.filename) : "[no active file]");
 	}
 }
 
@@ -178,7 +178,7 @@ static void observer_show_init_backtrace(zend_execute_data *execute_data)
 				php_printf("%*s%s()\n", indent, "", ZSTR_VAL(fbc->common.function_name));
 			}
 		} else {
-			php_printf("%*s{main} %s\n", indent, "", ZSTR_VAL(fbc->op_array.filename));
+			php_printf("%*s{main} %s\n", indent, "", fbc->op_array.filename ? ZSTR_VAL(fbc->op_array.filename) : "[no active file]");
 		}
 	} while ((ex = ex->prev_execute_data) != NULL);
 	php_printf("%*s-->\n", 2 * ZT_G(observer_nesting_depth), "");
diff --git a/ext/zend_test/tests/observer_fiber_backtrace_crash.phpt b/ext/zend_test/tests/observer_fiber_backtrace_crash.phpt
new file mode 100644
index 0000000000000..f19005179ac26
--- /dev/null
+++ b/ext/zend_test/tests/observer_fiber_backtrace_crash.phpt
@@ -0,0 +1,48 @@
+--TEST--
+GH-16319 (Fiber backtrace with null filename should not crash)
+--EXTENSIONS--
+zend_test
+--INI--
+zend_test.observer.enabled=1
+zend_test.observer.show_init_backtrace=1
+zend_test.observer.show_output=1
+zend_test.observer.observe_all=1
+zend_test.observer.show_opcode=0
+opcache.jit=0
+--FILE--
+<?php +$fiber = new Fiber(function() {}); +$fiber->start();
+echo "Test completed without crash\n";
+?>
+--EXPECTF--
+
+
+<file %s>
+ 
+ 
+ <fiber::__construct>
+ </fiber::__construct>
+ 
+ 
+ <fiber::start>
+ 
+ 
+ <{closure}>
+ </{closure}>
+ </fiber::start>
+Test completed without crash
+</file %s>
</div><div class="naked_ctrl">
<form action="/index.cgi/contrast" method="get" name="gate">
<p><a href="http://altstyle.alfasado.net">AltStyle</a> によって変換されたページ <a href="https://patch-diff.githubusercontent.com/raw/php/php-src/pull/19973.diff">(-&gt;オリジナル)</a>
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<option value="mobile">モバイル</option>
</select>
<input type="submit" value="表示" />
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