diff --git a/cue/export.go b/cue/export.go
index 40c58d0..7624fa9 100644
--- a/cue/export.go
+++ b/cue/export.go
@@ -554,7 +554,7 @@
 
 	case *bottom:
 		err := &ast.BottomLit{}
-		comment := &ast.Comment{Text: "// " + x.msg}
+		comment := &ast.Comment{Text: "/* " + x.msg + " */"}
 		err.AddComment(&ast.CommentGroup{
 			Line:     true,
 			Position: 1,
diff --git a/cue/export_test.go b/cue/export_test.go
index 68d59bd..e6a1f7c 100644
--- a/cue/export_test.go
+++ b/cue/export_test.go
@@ -67,9 +67,9 @@
 					s: "abc"
 				}
 				b: 2.0
-				c: _|_ // undefined field "c"
-				d: _|_ // undefined field "d"
-				e: _|_ // undefined field "t"
+				c: _|_ /* undefined field "c" */
+				d: _|_ /* undefined field "d" */
+				e: _|_ /* undefined field "t" */
 			}`),
 	}, {
 		in: `{