diff --git a/js/js.frontend/src/org/jetbrains/kotlin/js/descriptorUtils/descriptorUtils.kt b/js/js.frontend/src/org/jetbrains/kotlin/js/descriptorUtils/descriptorUtils.kt
index 0a1d7fad966..0805753abc7 100644
--- a/js/js.frontend/src/org/jetbrains/kotlin/js/descriptorUtils/descriptorUtils.kt
+++ b/js/js.frontend/src/org/jetbrains/kotlin/js/descriptorUtils/descriptorUtils.kt
@@ -20,7 +20,9 @@ val KotlinType.nameIfStandardType: Name?
     get() = constructor.declarationDescriptor?.takeIf(KotlinBuiltIns::isBuiltIn)?.name
 
 fun KotlinType.getJetTypeFqName(printTypeArguments: Boolean): String {
-    val declaration = requireNotNull(constructor.declarationDescriptor)
+    val declaration = requireNotNull(constructor.declarationDescriptor) {
+        "declarationDescriptor is null for constructor = $constructor with ${constructor.javaClass}"
+    }
     if (declaration is TypeParameterDescriptor) {
         return StringUtil.join(declaration.upperBounds, { type -> type.getJetTypeFqName(printTypeArguments) }, "&")
     }