diff --git a/ast/stdast.go b/ast/stdast.go
index b0b23d6..8ad08e0 100644
--- a/ast/stdast.go
+++ b/ast/stdast.go
@@ -4677,7 +4677,8 @@ var p1 = &Source{
 }
 
 // StdAst is the AST for the standard library.
-var StdAst = &DesugaredObject{
+var StdAst = _StdAst
+var _StdAst = &DesugaredObject{
 	NodeBase: NodeBase{
 		loc: LocationRange{
 			FileName: "<std>",
diff --git a/dump/dump.go b/dump/dump.go
index 8b24fe3..a9249ec 100644
--- a/dump/dump.go
+++ b/dump/dump.go
@@ -184,7 +184,21 @@ func (s *dumpState) dump(value interface{}) {
 	if v.Kind() == reflect.Ptr && v.IsNil() {
 		printNil(s.w)
 	} else {
+		// Replace the writer with a temporary buffer so that
+		// we can see how big the output is. If it's too big,
+		// we use an intermediate value so that godoc output
+		// isn't swamped by the literal.
+		oldWriter := s.w
+		buf := new(bytes.Buffer)
+		s.w = buf
 		s.dumpVal(v)
+		s.w = oldWriter
+		if buf.Len() > 100 {
+			s.w.Write([]byte("_" + s.config.VariableName))
+			s.newline()
+			s.w.Write([]byte("var _" + s.config.VariableName + " = "))
+		}
+		s.w.Write(buf.Bytes())
 	}
 	s.newline()
 }
diff --git a/dump/dump_test.go b/dump/dump_test.go
index 6c516a8..99b9881 100644
--- a/dump/dump_test.go
+++ b/dump/dump_test.go
@@ -454,3 +454,26 @@ var Obj = &struct { Foo *Zeo; Bar *Zeo }{
 		}
 	}
 }
+
+func TestSdumpLargeDefinition(t *testing.T) {
+	type largeStruct struct {
+		ABCDEFGHIJKLMNOBQRSTUVWXYZ0 int
+		ABCDEFGHIJKLMNOBQRSTUVWXYZ1 int
+		ABCDEFGHIJKLMNOBQRSTUVWXYZ2 int
+		ABCDEFGHIJKLMNOBQRSTUVWXYZ3 int
+		ABCDEFGHIJKLMNOBQRSTUVWXYZ4 int
+	}
+	got := Sdump(&largeStruct{1, 2, 3, 4, 5})
+	want := `var Obj = _Obj
+var _Obj = &largeStruct{
+	ABCDEFGHIJKLMNOBQRSTUVWXYZ0: int(1),
+	ABCDEFGHIJKLMNOBQRSTUVWXYZ1: int(2),
+	ABCDEFGHIJKLMNOBQRSTUVWXYZ2: int(3),
+	ABCDEFGHIJKLMNOBQRSTUVWXYZ3: int(4),
+	ABCDEFGHIJKLMNOBQRSTUVWXYZ4: int(5),
+}
+`
+	if got != want {
+		t.Errorf("got : \n%#v\n, want : \n%#v", got, want)
+	}
+}