diff --git a/src/ast.scm b/src/ast.scm
index d5016348c73c8..f5910933fc9c8 100644
--- a/src/ast.scm
+++ b/src/ast.scm
@@ -179,6 +179,13 @@
                               ""))
                         "")
                     (string.rep "    " ilvl) "end"))
+	   ((do)
+	    (let ((call (cadr e))
+		  (args (cdr (cadr (caddr e))))
+		  (body (caddr (caddr e))))
+	      (deparse-block (string (deparse call) " do" (if (null? args) "" " ")
+				     (deparse-arglist args))
+			     (cdr body) ilvl)))
            ((struct)
             (string (if (eq? (cadr e) 'true) "mutable " "")
                     "struct "
diff --git a/test/syntax.jl b/test/syntax.jl
index d8e2c96674cda..9f9f0d9687dde 100644
--- a/test/syntax.jl
+++ b/test/syntax.jl
@@ -1386,3 +1386,23 @@ end
 
 # issue #26717
 @test Meta.lower(@__MODULE__, :( :(:) = 2 )) == Expr(:error, "invalid assignment location \":(:)\"")
+
+# issue #17781
+let ex = Meta.lower(@__MODULE__, Meta.parse("
+    A = function (s, o...)
+        f(a, b) do
+        end
+    end,
+    B = function (s, o...)
+        f(a, b) do
+        end
+    end"))
+    @test isa(ex, Expr) && ex.head === :error
+    @test ex.args[1] == """
+invalid assignment location "function (s, o...)
+    # none, line 3
+    f(a, b) do
+        # none, line 4
+    end
+end\""""
+end