diff --git a/serde_derive_internals/src/check.rs b/serde_derive_internals/src/check.rs
index 229896cd..c3df861b 100644
--- a/serde_derive_internals/src/check.rs
+++ b/serde_derive_internals/src/check.rs
@@ -229,7 +229,7 @@ fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
 
     if type_tag == content_tag {
         let message = format!(
-            "Enum tags `{}` for type and content conflict with each other",
+            "enum tags `{}` for type and content conflict with each other",
             type_tag
         );
         cx.error(message);
diff --git a/test_suite/tests/compile-fail/conflict/adjacent-tag.rs b/test_suite/tests/compile-fail/conflict/adjacent-tag.rs
new file mode 100644
index 00000000..419afa4c
--- /dev/null
+++ b/test_suite/tests/compile-fail/conflict/adjacent-tag.rs
@@ -0,0 +1,20 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[serde(tag = "conflict", content = "conflict")]
+//~^^ HELP: enum tags `conflict` for type and content conflict with each other
+enum E {
+    A,
+    B,
+}
+
+fn main() {}
diff --git a/test_suite/tests/compile-fail/conflict/internal-tag.rs b/test_suite/tests/compile-fail/conflict/internal-tag.rs
new file mode 100644
index 00000000..777718bc
--- /dev/null
+++ b/test_suite/tests/compile-fail/conflict/internal-tag.rs
@@ -0,0 +1,22 @@
+// Copyright 2018 Serde Developers
+//
+// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
+// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
+// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
+// option. This file may not be copied, modified, or distributed
+// except according to those terms.
+
+#[macro_use]
+extern crate serde_derive;
+
+#[derive(Serialize)] //~ ERROR: proc-macro derive panicked
+#[serde(tag = "conflict")]
+//~^^ HELP: variant field name `conflict` conflicts with internal tag
+enum E {
+    A {
+        #[serde(rename = "conflict")]
+        x: (),
+    },
+}
+
+fn main() {}