diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 28e333964..3c379ea26 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -145,6 +145,7 @@ jobs:
           ./sbt -v --client doc
           ./sbt -v --client publishLocal
           ./sbt -v --client test
+          ./sbt -v --client lmCoursierShaded/test
           ./sbt -v --client "serverTestProj/test"
           ./sbt -v --client "all $UTIL_TESTS"
       - name: Build and test (2)
diff --git a/build.sbt b/build.sbt
index 09240ccb6..e9a26885d 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1333,6 +1333,8 @@ lazy val lmCoursier = project
   )
   .dependsOn(lmCore)
 
+lazy val checkLmcoursierPackage = taskKey[Unit]("")
+
 lazy val lmCoursierShaded = project
   .in(file("lm-coursier/target/shaded-module"))
   .settings(
@@ -1349,6 +1351,20 @@ lazy val lmCoursierShaded = project
     ),
     assembly / assemblyOption ~= { _.withIncludeScala(false) },
     conflictWarning := ConflictWarning.disable,
+    checkLmcoursierPackage := {
+      val jarFile = assembly.value
+      IO.withTemporaryDirectory { tmp =>
+        val notLmcoursierPackageClasses = IO
+          .unzip(jarFile, tmp, _.endsWith(".class"))
+          .toSeq
+          .map(f => IO.relativize(tmp, f).getOrElse(sys.error(s"invalid path ${f}")))
+          .filterNot(f => f.startsWith("lmcoursier") || f.startsWith("META-INF"))
+          .sorted
+        notLmcoursierPackageClasses.foreach(println)
+        assert(notLmcoursierPackageClasses.isEmpty)
+      }
+    },
+    Test / test := (Test / test).dependsOn(checkLmcoursierPackage).value,
     Utils.noPublish,
     assemblyShadeRules := {
       val namespacesToShade = Seq(