diff --git a/core/src/main/kotlin/net/corda/core/internal/AttachmentWithContext.kt b/core/src/main/kotlin/net/corda/core/internal/AttachmentWithContext.kt
index fdfb135aca..8ecc2a0373 100644
--- a/core/src/main/kotlin/net/corda/core/internal/AttachmentWithContext.kt
+++ b/core/src/main/kotlin/net/corda/core/internal/AttachmentWithContext.kt
@@ -16,7 +16,7 @@ class AttachmentWithContext(
 ) : Attachment by contractAttachment {
     init {
         require(contract in contractAttachment.allContracts) {
-            "This AttachmentWithContext was not initialised properly"
+            "This AttachmentWithContext was not initialised properly. Please ensure all Corda contracts extending existing Corda contracts also implement the Contract base class."
         }
     }
 }
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