diff --git a/gcc/cp/ChangeLog b/gcc/cp/ChangeLog
index 8e723be3eba8..35f0a2222ac2 100644
--- a/gcc/cp/ChangeLog
+++ b/gcc/cp/ChangeLog
@@ -1,3 +1,9 @@
+2017-01-05  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/78765
+	* pt.c (convert_nontype_argument): Don't try and see if integral
+	or enum expressions are constants prematurely.
+
 2017-01-04  Marek Polacek  <polacek@redhat.com>
 
 	PR c++/64767
diff --git a/gcc/cp/pt.c b/gcc/cp/pt.c
index 51c3c57b009f..366c59a2486a 100644
--- a/gcc/cp/pt.c
+++ b/gcc/cp/pt.c
@@ -6386,7 +6386,7 @@ convert_nontype_argument (tree type, tree expr, tsubst_flags_t complain)
 	   to leave it in that form rather than lower it to a
 	   CONSTRUCTOR.  */;
       else if (INTEGRAL_OR_ENUMERATION_TYPE_P (type))
-	expr = maybe_constant_value (expr);
+	/* Constant value checking is done later with type conversion.  */;
       else if (cxx_dialect >= cxx1z)
 	{
 	  if (TREE_CODE (type) != REFERENCE_TYPE)
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 86dee20ddb8b..aa6dc348cc39 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,8 @@
+2017-01-05  Nathan Sidwell  <nathan@acm.org>
+
+	PR c++/78765
+	* g++.dg/cpp0x/pr78765.C: New.
+
 2017-01-05  Dominik Vogt  <vogt@linux.vnet.ibm.com>
 
 	* gcc.target/s390/memcpy-2.c: New test.
diff --git a/gcc/testsuite/g++.dg/cpp0x/pr78765.C b/gcc/testsuite/g++.dg/cpp0x/pr78765.C
new file mode 100644
index 000000000000..6b66d26e5497
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/pr78765.C
@@ -0,0 +1,15 @@
+// PR c++/78765
+// { dg-do compile { target c++11 } }
+
+// ICE with failed constexpr object and member fn call
+
+struct ValueType {
+  constexpr operator int() const {return field;}
+  int field;
+};
+
+static constexpr ValueType var = 0; // { dg-error "conversion" }
+
+template <int> class ValueTypeInfo;
+
+ValueTypeInfo<var> x;