diff --git a/gcc/cp/constexpr.cc b/gcc/cp/constexpr.cc
index e4c435fecbef566d9ba7daf33bc10151eb93e3d6..2c5c9d99b34aea515967fe9712a123ef79b47dd4 100644
--- a/gcc/cp/constexpr.cc
+++ b/gcc/cp/constexpr.cc
@@ -9207,7 +9207,12 @@ potential_constant_expression_1 (tree t, bool want_rval, bool strict, bool now,
 	  }
 	else if (fun)
           {
-	    if (RECUR (fun, FUNCTION_POINTER_TYPE_P (fun) ? rval : any))
+	    if (TREE_TYPE (fun)
+		&& FUNCTION_POINTER_TYPE_P (TREE_TYPE (fun)))
+	      want_rval = rval;
+	    else
+	      want_rval = any;
+	    if (RECUR (fun, want_rval))
 	      /* Might end up being a constant function pointer.  But it
 		 could also be a function object with constexpr op(), so
 		 we pass 'any' so that the underlying VAR_DECL is deemed
diff --git a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C
index 3f63a5b28d70c9e06443fc3cf8dfce7aa1217302..c63d26c931d9e3e7dbdca4b0ac74a715a98d0c25 100644
--- a/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C
+++ b/gcc/testsuite/g++.dg/cpp2a/concepts-fn8.C
@@ -15,10 +15,12 @@ struct P {
 };
 
 void (*f)(P);
+P (*h)(P);
 
 template<class T>
 constexpr bool g() {
   P x;
   f(x); // { dg-bogus "from here" }
+  f(h(x)); // { dg-bogus "from here" }
   return true;
 }
diff --git a/gcc/testsuite/g++.dg/diagnostic/constexpr4.C b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C
new file mode 100644
index 0000000000000000000000000000000000000000..f37c01cac55abf140f44f16fc6070d21055ea6da
--- /dev/null
+++ b/gcc/testsuite/g++.dg/diagnostic/constexpr4.C
@@ -0,0 +1,9 @@
+// Verify we diagnose a call to a non-constant function pointer ahead of time.
+// { dg-do compile { target c++11 } }
+
+bool (*f)(int);
+
+template<int N>
+void g() {
+  static_assert(f(N), ""); // { dg-error "non-constant|'f' is not usable" }
+}