diff --git a/gcc/cp/call.c b/gcc/cp/call.c
index 123f06b1f2b..7d12fea60f2 100644
--- a/gcc/cp/call.c
+++ b/gcc/cp/call.c
@@ -1449,7 +1449,9 @@ standard_conversion (tree to, tree from, tree expr, bool c_cast_p,
       tree fbase = class_of_this_parm (fromfn);
       tree tbase = class_of_this_parm (tofn);
 
-      if (!DERIVED_FROM_P (fbase, tbase))
+      /* If FBASE and TBASE are equivalent but incomplete, DERIVED_FROM_P
+	 yields false.  But a pointer to member of incomplete class is OK.  */
+      if (!same_type_p (fbase, tbase) && !DERIVED_FROM_P (fbase, tbase))
 	return NULL;
 
       tree fstat = static_fn_type (fromfn);
diff --git a/gcc/testsuite/g++.dg/cpp1z/noexcept-type23.C b/gcc/testsuite/g++.dg/cpp1z/noexcept-type23.C
new file mode 100644
index 00000000000..612dd6ceb5e
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp1z/noexcept-type23.C
@@ -0,0 +1,14 @@
+// PR c++/99374
+// { dg-do compile { target c++17 } }
+
+struct S;
+struct R;
+using F1 = int (S::*)();
+using F2 = int (S::*)() noexcept;
+using F3 = int (R::*)() noexcept;
+using T = S;
+using F4 = int (T::*)() noexcept;
+F1 f21 = F2();
+F1 f41 = F4();
+F2 f12 = F1(); // { dg-error "cannot convert" }
+F1 f31 = F3(); // { dg-error "cannot convert" }