diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index 8f7f0b7d325..9122a5efa65 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -2897,7 +2897,7 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
 
   /* We can't defer instantiating the function any longer.  */
   if (!DECL_INITIAL (fun)
-      && DECL_TEMPLOID_INSTANTIATION (fun)
+      && (DECL_TEMPLOID_INSTANTIATION (fun) || DECL_DEFAULTED_FN (fun))
       && !uid_sensitive_constexpr_evaluation_p ())
     {
       location_t save_loc = input_location;
@@ -2905,7 +2905,10 @@ cxx_eval_call_expression (const constexpr_ctx *ctx, tree t,
       ++function_depth;
       if (ctx->manifestly_const_eval == mce_true)
 	FNDECL_MANIFESTLY_CONST_EVALUATED (fun) = true;
-      instantiate_decl (fun, /*defer_ok*/false, /*expl_inst*/false);
+      if (DECL_TEMPLOID_INSTANTIATION (fun))
+	instantiate_decl (fun, /*defer_ok*/false, /*expl_inst*/false);
+      else
+	synthesize_method (fun);
       --function_depth;
       input_location = save_loc;
     }
@@ -8110,11 +8113,14 @@ instantiate_cx_fn_r (tree *tp, int *walk_subtrees, void */*data*/)
       && DECL_DECLARED_CONSTEXPR_P (*tp)
       && !DECL_INITIAL (*tp)
       && !trivial_fn_p (*tp)
-      && DECL_TEMPLOID_INSTANTIATION (*tp)
+      && (DECL_TEMPLOID_INSTANTIATION (*tp) || DECL_DEFAULTED_FN (*tp))
       && !uid_sensitive_constexpr_evaluation_p ())
     {
       ++function_depth;
-      instantiate_decl (*tp, /*defer_ok*/false, /*expl_inst*/false);
+      if (DECL_TEMPLOID_INSTANTIATION (*tp))
+	instantiate_decl (*tp, /*defer_ok*/false, /*expl_inst*/false);
+      else
+	synthesize_method (*tp);
       --function_depth;
     }
   else if (TREE_CODE (*tp) == CALL_EXPR
diff --git a/gcc/testsuite/g++.dg/cpp2a/nontype-class59.C b/gcc/testsuite/g++.dg/cpp2a/nontype-class59.C
new file mode 100644
index 00000000000..6e40698da2f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp2a/nontype-class59.C
@@ -0,0 +1,23 @@
+// PR c++/110122
+// { dg-do compile { target c++20 } }
+
+struct Foo {
+  Foo() = default;
+  constexpr Foo(const Foo&) { }
+};
+
+struct Bar {
+  Foo _;
+};
+
+template<Bar V>
+struct A { };
+
+template<Bar V>
+void f() {
+  [](auto){ A<V> d; }(0); // { dg-bogus "used before its definition" }
+};
+
+int main() {
+  f<Bar{}>();
+}