diff --git a/libstdc++-v3/ChangeLog b/libstdc++-v3/ChangeLog
index 6be181413ff..7bb093de366 100644
--- a/libstdc++-v3/ChangeLog
+++ b/libstdc++-v3/ChangeLog
@@ -1,5 +1,9 @@
 2019-09-10  Jonathan Wakely  <jwakely@redhat.com>
 
+	PR libstdc++/91711
+	* testsuite/23_containers/span/get_neg.cc: Avoid ambiguity due to
+	0ul being a valid null pointer constant.
+
 	* include/std/type_traits (__remove_cv_t): New alias template.
 	(is_void, is_integral, is_floating_point, is_pointer)
 	(is_member_object_pointer, is_member_function_pointer, is_null_pointer)
diff --git a/libstdc++-v3/testsuite/23_containers/span/get_neg.cc b/libstdc++-v3/testsuite/23_containers/span/get_neg.cc
index 37d188ed073..cd54716b105 100644
--- a/libstdc++-v3/testsuite/23_containers/span/get_neg.cc
+++ b/libstdc++-v3/testsuite/23_containers/span/get_neg.cc
@@ -24,7 +24,7 @@
 int
 main()
 {
-  std::span<int, std::dynamic_extent> myspan((int*)nullptr, 0ul);
+  std::span<int, std::dynamic_extent> myspan((int*)nullptr, (std::size_t)0);
   std::get<0>(myspan); // { dg-error "here" }
 }
 // { dg-error "static assertion failed" "" { target *-*-* } 0 }