diff --git a/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeCronLaws.scala b/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeCronLaws.scala
index ad075d7d..c3ff6e67 100644
--- a/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeCronLaws.scala
+++ b/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeCronLaws.scala
@@ -76,7 +76,7 @@ object DateTimeCronLaws {
       TC0: DateTimeCron[E]
   ): DateTimeCronLaws[E, DateTime] =
     new DateTimeCronLaws[E, DateTime] {
-      implicit val DT = dt0
-      implicit val TC = TC0
+      implicit val DT: IsDateTime[DateTime] = dt0
+      implicit val TC: DateTimeCron[E]      = TC0
     }
 }
diff --git a/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeNodeLaws.scala b/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeNodeLaws.scala
index f778683a..7c37599c 100644
--- a/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeNodeLaws.scala
+++ b/modules/testkit/shared/src/main/scala/cron4s/testkit/laws/DateTimeNodeLaws.scala
@@ -51,8 +51,8 @@ object DateTimeNodeLaws {
       TC0: DateTimeNode[E, F]
   ): DateTimeNodeLaws[E, F, DateTime] =
     new DateTimeNodeLaws[E, F, DateTime] {
-      implicit val DT   = dt0
-      implicit val expr = expr0
-      implicit val TC   = TC0
+      implicit val DT: IsDateTime[DateTime] = dt0
+      implicit val expr: FieldExpr[E, F]    = expr0
+      implicit val TC: DateTimeNode[E, F]   = TC0
     }
 }