diff --git a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
index 7744656d67b..631c1960ba5 100644
--- a/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
+++ b/Interop/StubGenerator/src/main/kotlin/org/jetbrains/kotlin/native/interop/gen/jvm/main.kt
@@ -142,6 +142,18 @@ private fun Properties.storeProperties(file: File) {
     }
 }
 
+private fun Properties.putAndRunOnReplace(key: Any, newValue: Any, beforeReplace: (Any, Any, Any) -> Unit) {
+    val oldValue = this[key]
+    if (oldValue != null && oldValue!! != newValue) {
+        beforeReplace(key, oldValue!!, newValue)
+    }
+    this[key] = newValue
+}
+
+private fun warn(msg: String) {
+    println("warning: $msg")
+}
+
 private fun usage() {
     println("""
 Run interop tool with -def <def_file_for_lib>.def
@@ -318,7 +330,13 @@ private fun processLib(args: Map<String, List<String>>,
 
     // TODO: if a library has partially included headers, then it shouldn't be used as a dependency.
     def.manifestAddendProperties["includedHeaders"] = nativeIndex.includedHeaders.joinToString(" ") { it.value }
-    def.manifestAddendProperties["pkg"] = outKtPkg
+
+    def.manifestAddendProperties.putAndRunOnReplace("package", outKtPkg) {
+        key, oldValue, newValue ->
+            warn("The package value `$oldValue` specified in .def file is overriden with explicit $newValue")
+    }
+
+    def.manifestAddendProperties["interop"] = "true"
 
     gen.addManifestProperties(def.manifestAddendProperties)
 
diff --git a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InteropUtils.kt b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InteropUtils.kt
index 81df0a9f521..6fd0a2fdb08 100644
--- a/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InteropUtils.kt
+++ b/backend.native/compiler/ir/backend.native/src/org/jetbrains/kotlin/backend/konan/InteropUtils.kt
@@ -39,7 +39,9 @@ interface InteropLibrary {
 }
 
 fun createInteropLibrary(reader: KonanLibraryReader): InteropLibrary? {
-    val pkg = reader.manifestProperties.getProperty("pkg") ?: return null
+    if (reader.manifestProperties.getProperty("interop") != "true") return null
+    val pkg = reader.manifestProperties.getProperty("package") 
+        ?: error("Inconsistent manifest: interop library ${reader.libraryName} should have `package` specified")
     val exportForwardDeclarations = reader.manifestProperties
             .getProperty("exportForwardDeclarations").split(' ')
             .map { it.trim() }.filter { it.isNotEmpty() }
diff --git a/utilities/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/main.kt b/utilities/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/main.kt
index 18475d8e49e..92f86178db8 100644
--- a/utilities/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/main.kt
+++ b/utilities/src/main/kotlin/org/jetbrains/kotlin/cli/utilities/main.kt
@@ -69,7 +69,7 @@ fun invokeCinterop(args: Array<String>) {
         val library = KonanLibrary(it.libraryFile)
         val manifestProperties = library.manifestFile.loadProperties()
         // TODO: handle missing properties?
-        manifestProperties["pkg"]?.let {
+        manifestProperties["package"]?.let {
             val pkg = it as String
             val headerIds = (manifestProperties["includedHeaders"] as String).split(' ')
             val arg = "$pkg:${headerIds.joinToString(",")}"