diff --git a/gcc/cp/expr.cc b/gcc/cp/expr.cc
index 31fe0980337..56fc11f425b 100644
--- a/gcc/cp/expr.cc
+++ b/gcc/cp/expr.cc
@@ -397,6 +397,11 @@ fold_for_warn (tree x)
 {
   /* C++ implementation.  */
 
+  if (cp_unevaluated_operand)
+    /* In an unevaluated context we don't care about the reduced value
+       of an expression, so neither should any warnings.  */
+    return x;
+
   /* Prevent warning-dependent constexpr evaluation from changing
      DECL_UID (which breaks -fcompare-debug) and from instantiating
      templates.  */
diff --git a/gcc/testsuite/g++.dg/cpp0x/decltype82a.C b/gcc/testsuite/g++.dg/cpp0x/decltype82a.C
new file mode 100644
index 00000000000..cbbcdfd8e58
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/decltype82a.C
@@ -0,0 +1,11 @@
+// PR c++/105931
+// { dg-do compile { target c++11 } }
+// A version of decltype82.C where N is unsigned.
+
+template<unsigned N>
+void f() {
+  using ty1 = decltype((5 % N) == 0);
+  using ty2 = decltype((5 / N) == 0);
+}
+
+template void f<0>();