diff --git a/gcc/cp/call.cc b/gcc/cp/call.cc
index 951b9fd2a88dea0aa66d73762d979c63cf65aeff..c7c7a122045cf868c526320ba3a3534e37839529 100644
--- a/gcc/cp/call.cc
+++ b/gcc/cp/call.cc
@@ -13539,6 +13539,13 @@ maybe_warn_dangling_reference (const_tree decl, tree init)
     return;
   if (!TYPE_REF_P (TREE_TYPE (decl)))
     return;
+  /* Don't suppress the diagnostic just because the call comes from
+     a system header.  If the DECL is not in a system header, or if
+     -Wsystem-headers was provided, warn.  */
+  auto wsh
+    = make_temp_override (global_dc->dc_warn_system_headers,
+			  (!in_system_header_at (DECL_SOURCE_LOCATION (decl))
+			   || global_dc->dc_warn_system_headers));
   if (tree call = do_warn_dangling_reference (init))
     {
       auto_diagnostic_group d;
diff --git a/gcc/testsuite/g++.dg/warn/Wdangling-reference4.C b/gcc/testsuite/g++.dg/warn/Wdangling-reference4.C
new file mode 100644
index 0000000000000000000000000000000000000000..aee7a29019b9a6ba5c70f4ba878e192528e1a21a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wdangling-reference4.C
@@ -0,0 +1,14 @@
+// { dg-do compile { target c++17 } }
+// { dg-options "-Wdangling-reference" }
+// Check that we warn here even without -Wsystem-headers.
+
+#include <optional>
+#include <string>
+
+auto f() -> std::optional<std::string>;
+
+void
+g ()
+{
+  for (char c : f().value()) { (void) c; } // { dg-warning "dangling reference" }
+}