diff --git a/compiler/src/dotty/tools/dotc/transform/sjs/PrepJSInterop.scala b/compiler/src/dotty/tools/dotc/transform/sjs/PrepJSInterop.scala
index d934dc179989..8a430991e378 100644
--- a/compiler/src/dotty/tools/dotc/transform/sjs/PrepJSInterop.scala
+++ b/compiler/src/dotty/tools/dotc/transform/sjs/PrepJSInterop.scala
@@ -888,6 +888,9 @@ class PrepJSInterop extends MacroTransform with IdentityDenotTransformer { thisP
             report.error("A non-native JS trait cannot contain private members", tree)
           } else if (sym.is(Lazy)) {
             report.error("A non-native JS trait cannot contain lazy vals", tree)
+          } else if (sym.is(ParamAccessor)) {
+            // #12621
+            report.error("A non-native JS trait cannot have constructor parameters", tree)
           } else if (!sym.is(Deferred)) {
             /* Tell the back-end not to emit this thing. In fact, this only
              * matters for mixed-in members created from this member.
diff --git a/tests/neg-scalajs/js-trait-ctor-param.check b/tests/neg-scalajs/js-trait-ctor-param.check
new file mode 100644
index 000000000000..bc5296b3c76f
--- /dev/null
+++ b/tests/neg-scalajs/js-trait-ctor-param.check
@@ -0,0 +1,4 @@
+-- Error: tests/neg-scalajs/js-trait-ctor-param.scala:9:34 -------------------------------------------------------------
+9 |trait NonNativeBagHolderTrait(val bag: Bag) extends js.Any // error
+  |                              ^^^^^^^^^^^^
+  |                              A non-native JS trait cannot have constructor parameters
diff --git a/tests/neg-scalajs/js-trait-ctor-param.scala b/tests/neg-scalajs/js-trait-ctor-param.scala
new file mode 100644
index 000000000000..c907b0d9b606
--- /dev/null
+++ b/tests/neg-scalajs/js-trait-ctor-param.scala
@@ -0,0 +1,9 @@
+import scala.scalajs.js
+import scala.scalajs.js.annotation.*
+
+@js.native
+trait Bag extends js.Any {
+  val str: String
+}
+
+trait NonNativeBagHolderTrait(val bag: Bag) extends js.Any // error