diff --git a/gcc/cp/mangle.cc b/gcc/cp/mangle.cc
index 826c5e76c1d..7dab4e62bc9 100644
--- a/gcc/cp/mangle.cc
+++ b/gcc/cp/mangle.cc
@@ -3402,6 +3402,11 @@ write_expression (tree expr)
       else
 	write_string ("tr");
     }
+  else if (code == NOEXCEPT_EXPR)
+    {
+      write_string ("nx");
+      write_expression (TREE_OPERAND (expr, 0));
+    }
   else if (code == CONSTRUCTOR)
     {
       bool braced_init = BRACE_ENCLOSED_INITIALIZER_P (expr);
diff --git a/gcc/testsuite/g++.dg/abi/mangle78.C b/gcc/testsuite/g++.dg/abi/mangle78.C
new file mode 100644
index 00000000000..63c4d779e9f
--- /dev/null
+++ b/gcc/testsuite/g++.dg/abi/mangle78.C
@@ -0,0 +1,14 @@
+// PR c++/70790
+// { dg-do compile { target c++11 } }
+
+template<bool B>
+struct A { };
+
+template<class T>
+void f(A<noexcept(T{})>);
+
+int main() {
+  f<int>({});
+}
+
+// { dg-final { scan-assembler "_Z1fIiEv1AIXnxtlT_EEE" } }
diff --git a/libiberty/cp-demangle.c b/libiberty/cp-demangle.c
index f2b36bcad68..18ab28fd028 100644
--- a/libiberty/cp-demangle.c
+++ b/libiberty/cp-demangle.c
@@ -1947,6 +1947,7 @@ const struct demangle_operator_info cplus_demangle_operators[] =
   { "ng", NL ("-"),         1 },
   { "nt", NL ("!"),         1 },
   { "nw", NL ("new"),       3 },
+  { "nx", NL ("noexcept"),  1 },
   { "oR", NL ("|="),        2 },
   { "oo", NL ("||"),        2 },
   { "or", NL ("|"),         2 },
@@ -5836,8 +5837,8 @@ d_print_comp_inner (struct d_print_info *dpi, int options,
 	if (code && !strcmp (code, "gs"))
 	  /* Avoid parens after '::'.  */
 	  d_print_comp (dpi, options, operand);
-	else if (code && !strcmp (code, "st"))
-	  /* Always print parens for sizeof (type).  */
+	else if (code && (!strcmp (code, "st") || !strcmp (code, "nx")))
+	  /* Always print parens for sizeof (type) and noexcept(expr).  */
 	  {
 	    d_append_char (dpi, '(');
 	    d_print_comp (dpi, options, operand);
diff --git a/libiberty/testsuite/demangle-expected b/libiberty/testsuite/demangle-expected
index d9bc7ed4b1f..52dff883a18 100644
--- a/libiberty/testsuite/demangle-expected
+++ b/libiberty/testsuite/demangle-expected
@@ -1659,3 +1659,6 @@ auto f()::{lambda<typename $T0>(X<$T0>*, X<int>*)#1}::operator()<char>(X<char>*,
 
 _ZZN1XIiE1FEvENKUliE_clEi
 X<int>::F()::{lambda(int)#1}::operator()(int) const
+
+_Z1fIiEv1AIXnxtlT_EEE
+void f<int>(A<noexcept(int{})>)