diff --git a/gcc/cp/typeck.c b/gcc/cp/typeck.c
index 8535ecc2d93..11dee7d8753 100644
--- a/gcc/cp/typeck.c
+++ b/gcc/cp/typeck.c
@@ -10215,6 +10215,9 @@ check_return_expr (tree retval, bool *no_warning)
     dependent:
       /* We should not have changed the return value.  */
       gcc_assert (retval == saved_retval);
+      /* We don't know if this is an lvalue or rvalue use, but
+	 either way we can mark it as read.  */
+      mark_exp_read (retval);
       return retval;
     }
 
diff --git a/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C
new file mode 100644
index 00000000000..b43cbe6b675
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1y/lambda-generic-Wunused.C
@@ -0,0 +1,18 @@
+// PR c++/96311
+// { dg-do compile { target c++14 } }
+// { dg-additional-options -Wunused }
+
+auto foo()
+{
+  constexpr int used = 0;
+  return
+    [](auto unused)
+    {
+      return used;
+    };
+}
+
+int main()
+{
+  foo()(42);
+}