diff --git a/core/src/main/kotlin/com/r3corda/core/Utils.kt b/core/src/main/kotlin/com/r3corda/core/Utils.kt
index 9df261181d..80248cf812 100644
--- a/core/src/main/kotlin/com/r3corda/core/Utils.kt
+++ b/core/src/main/kotlin/com/r3corda/core/Utils.kt
@@ -13,7 +13,6 @@ import rx.Observable
 import rx.subjects.UnicastSubject
 import java.io.BufferedInputStream
 import java.io.InputStream
-import java.lang.Comparable
 import java.math.BigDecimal
 import java.nio.file.Files
 import java.nio.file.LinkOption
@@ -293,7 +292,7 @@ fun <T, I: Comparable<I>> Iterable<T>.isOrderedAndUnique(extractId: T.() -> I):
         if (lastLast == null) {
             true
         } else {
-            lastLast.compareTo(extractId(it)) < 0
+            lastLast < extractId(it)
         }
     }
 }
\ No newline at end of file
diff --git a/core/src/test/kotlin/com/r3corda/core/UtilsTest.kt b/core/src/test/kotlin/com/r3corda/core/UtilsTest.kt
new file mode 100644
index 0000000000..ea3191fdab
--- /dev/null
+++ b/core/src/test/kotlin/com/r3corda/core/UtilsTest.kt
@@ -0,0 +1,24 @@
+package com.r3corda.core
+
+import kotlin.test.assertFalse
+import kotlin.test.assertTrue
+
+class UtilsTest {
+    fun `ordered and unique basic`() {
+        val basic = listOf(1, 2, 3, 5, 8)
+        assertTrue(basic.isOrderedAndUnique { this })
+
+        val negative = listOf(-1, 2, 5)
+        assertTrue(negative.isOrderedAndUnique { this })
+    }
+
+    fun `ordered and unique duplicate`() {
+        val duplicated = listOf(1, 2, 2, 3, 5, 8)
+        assertFalse(duplicated.isOrderedAndUnique { this })
+    }
+
+    fun `ordered and unique out of sequence`() {
+        val mixed = listOf(3, 1, 2, 8, 5)
+        assertFalse(mixed.isOrderedAndUnique { this })
+    }
+}
\ No newline at end of file