diff --git a/cue/ast.go b/cue/ast.go
index 4b9b193..c2bb876 100644
--- a/cue/ast.go
+++ b/cue/ast.go
@@ -297,8 +297,15 @@
 
 		arcs := []arc{}
 		for i, e := range elts {
+			elem := v1.walk(e)
+			if elem == nil {
+				// TODO: it would be consistent to allow aliasing in lists
+				// as well, with a similar meaning as alias declarations in
+				// structs.
+				return v.errf(n, "alias not allowed in list")
+			}
 			v1.sel = strconv.Itoa(i)
-			arcs = append(arcs, arc{feature: label(i), v: v1.walk(e)})
+			arcs = append(arcs, arc{feature: label(i), v: elem})
 		}
 		s := &structLit{baseValue: newExpr(n), arcs: arcs}
 		list := &list{baseValue: newExpr(n), elem: s}
diff --git a/cue/ast_test.go b/cue/ast_test.go
index 7772fcb..9417ea6 100644
--- a/cue/ast_test.go
+++ b/cue/ast_test.go
@@ -370,6 +370,14 @@
 		out: `<0>{` +
 			`def :: (<1>C{Size: int, Type: string, Text: string} & (<2>C{Size: 0, Type: "B"} | <3>C{Size: 1, Type: "A"}))` +
 			`}`,
+	}, {
+		// Issue #172
+		in: `
+		package testenv
+		env_:: [NAME=_]: [VALUE=_]
+		env_:: foo: "bar"
+			`,
+		out: "env_.*: alias not allowed in list:\n    test:3:20\n<0>{}",
 	}}
 	for _, tc := range testCases {
 		t.Run("", func(t *testing.T) {