diff --git a/compiler/rename/RnTypes.hs b/compiler/rename/RnTypes.hs
index 35b67a2fd1b0305ca179f1b93fe447f1ba865e3b..014d4850c85379011aa4c69665610a56f6319534 100644
--- a/compiler/rename/RnTypes.hs
+++ b/compiler/rename/RnTypes.hs
@@ -1431,8 +1431,9 @@ sectionPrecErr op@(n1,_) arg_op@(n2,_) section
          nest 4 (text "in the section:" <+> quotes (ppr section))]
 
 is_unbound :: OpName -> Bool
-is_unbound UnboundOp{} = True
-is_unbound _           = False
+is_unbound (NormalOp n) = isUnboundName n
+is_unbound UnboundOp{}  = True
+is_unbound _            = False
 
 ppr_opfix :: (OpName, Fixity) -> SDoc
 ppr_opfix (op, fixity) = pp_op <+> brackets (ppr fixity)
diff --git a/testsuite/tests/rename/should_fail/T13947.hs b/testsuite/tests/rename/should_fail/T13947.hs
new file mode 100644
index 0000000000000000000000000000000000000000..bc435e70eb9add5ac08e559360d24c41d5443fb5
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/T13947.hs
@@ -0,0 +1,5 @@
+{-# LANGUAGE TypeOperators #-}
+module T13947 where
+
+f :: () -> Int :~: Int
+f = undefined
diff --git a/testsuite/tests/rename/should_fail/T13947.stderr b/testsuite/tests/rename/should_fail/T13947.stderr
new file mode 100644
index 0000000000000000000000000000000000000000..8a636a2bb98789c8dcf217256c7250d037e8f5bd
--- /dev/null
+++ b/testsuite/tests/rename/should_fail/T13947.stderr
@@ -0,0 +1,3 @@
+
+T13947.hs:4:12: error:
+    Not in scope: type constructor or class ‘:~:’
diff --git a/testsuite/tests/rename/should_fail/all.T b/testsuite/tests/rename/should_fail/all.T
index 457f4010b1273564cd3b87afea9f067bbaa51dfc..f7f77192c846411ed651e40c1d0a21ad842653f2 100644
--- a/testsuite/tests/rename/should_fail/all.T
+++ b/testsuite/tests/rename/should_fail/all.T
@@ -127,3 +127,4 @@ test('T11592', normal, compile_fail, [''])
 test('T12879', normal, compile_fail, [''])
 test('T13644', expect_broken(13644), multimod_compile_fail, ['T13644','-v0'])
 test('T13568', normal, multimod_compile_fail, ['T13568','-v0'])
+test('T13947', normal, compile_fail, [''])