diff --git a/cue/ast/astutil/resolve.go b/cue/ast/astutil/resolve.go
index 6f923fb..af8cbd3 100644
--- a/cue/ast/astutil/resolve.go
+++ b/cue/ast/astutil/resolve.go
@@ -45,10 +45,11 @@
 // scope.
 //
 type scope struct {
-	file  *ast.File
-	outer *scope
-	node  ast.Node
-	index map[string]ast.Node
+	file    *ast.File
+	outer   *scope
+	node    ast.Node
+	index   map[string]ast.Node
+	inField bool
 
 	errFn func(p token.Pos, msg string, args ...interface{})
 }
@@ -208,7 +209,7 @@
 			if len(label.Elts) != 1 {
 				break
 			}
-			s := newScope(s.file, s, x, nil)
+			s = newScope(s.file, s, x, nil)
 			if alias != nil {
 				if name, _, _ := ast.LabelName(alias.Ident); name != "" {
 					s.insert(name, x)
@@ -231,22 +232,33 @@
 					s.insert(name, a.Expr)
 				}
 			}
+
+			ast.Walk(expr, nil, func(n ast.Node) {
+				if x, ok := n.(*ast.Ident); ok {
+					for s := s; s != nil && !s.inField; s = s.outer {
+						if _, ok := s.index[x.Name]; ok {
+							s.errFn(n.Pos(),
+								"reference %q in label expression refers to field against which it would be matched", x.Name)
+						}
+					}
+				}
+			})
 			walk(s, expr)
-			walk(s, x.Value)
-			return nil
 
 		case *ast.TemplateLabel:
-			s := newScope(s.file, s, x, nil)
+			s = newScope(s.file, s, x, nil)
 			name, err := ast.ParseIdent(label.Ident)
 			if err == nil {
 				s.insert(name, x.Label) // Field used for entire lambda.
 			}
-			walk(s, x.Value)
-			return nil
 		}
+
 		if x.Value != nil {
+			s.inField = true
 			walk(s, x.Value)
+			s.inField = false
 		}
+
 		return nil
 
 	case *ast.Alias:
diff --git a/cue/ast_test.go b/cue/ast_test.go
index 87f93dd..240105f 100644
--- a/cue/ast_test.go
+++ b/cue/ast_test.go
@@ -230,14 +230,28 @@
 		// optional fields with key filters
 		in: `
 			JobID: =~"foo"
-			[JobID]: { name: string }
+			a: [JobID]: { name: string }
 
 			[<"s"]: { other: string }
 			`,
 		out: `<0>{` +
-			`[<0>.JobID]: <1>(_: string)-><2>{name: string}, ` +
-			`[<"s"]: <3>(_: string)-><4>{other: string}, ` +
-			`JobID: =~"foo"}`,
+			`[<"s"]: <1>(_: string)-><2>{other: string}, ` +
+			`JobID: =~"foo", a: <3>{` +
+			`[<0>.JobID]: <4>(_: string)-><5>{name: string}, ` +
+			`}}`,
+	}, {
+		// Issue #251
+		// TODO: the is one of the cases where it is relatively easy to catch
+		// a structural cycle. We should be able, however, to break the cycle
+		// with a post-validation constraint. Clean this up with the evaluator
+		// update.
+		in: `
+		{
+			[x]: 3
+		}
+		x:   "x"
+		`,
+		out: "reference \"x\" in label expression refers to field against which it would be matched:\n    test:3:5\n<0>{}",
 	}, {
 		// illegal alias usage
 		in: `