diff --git a/build.sbt b/build.sbt
index bdab851..0a62155 100644
--- a/build.sbt
+++ b/build.sbt
@@ -1,4 +1,5 @@
-import sbtcrossproject.CrossPlugin.autoImport.{crossProject, CrossType}
+import com.typesafe.tools.mima.core.{IncompatibleSignatureProblem, ProblemFilters}
+import sbtcrossproject.CrossPlugin.autoImport.{CrossType, crossProject}
 
 ThisBuild / organization := "org.julienrf"
 
@@ -10,6 +11,11 @@ ThisBuild / versionPolicyIntention := Compatibility.BinaryAndSourceCompatible
 // Temporary, because version 10.0.0 was invalid
 ThisBuild / versionPolicyPreviousVersions := Seq("10.0.1")
 
+ThisBuild / mimaBinaryIssueFilters ++= Seq(
+  // package private method
+  ProblemFilters.exclude[IncompatibleSignatureProblem]("julienrf.json.derived.DerivedOWritesUtil.makeCoProductOWrites")
+)
+
 ThisBuild / developers := List(
   Developer(
     "julienrf",
diff --git a/library/src/main/scala/julienrf/json/derived/DerivedOWrites.scala b/library/src/main/scala/julienrf/json/derived/DerivedOWrites.scala
index b83a221..2e2e6c0 100644
--- a/library/src/main/scala/julienrf/json/derived/DerivedOWrites.scala
+++ b/library/src/main/scala/julienrf/json/derived/DerivedOWrites.scala
@@ -32,7 +32,7 @@ trait DerivedOWritesInstances extends DerivedOWritesInstances1 {
     typeTag: TT[FieldType[K, L]]
   ): DerivedOWrites[FieldType[K, L] :+: R, TT] =
     DerivedOWritesUtil.makeCoProductOWrites(
-      (_, _) => writesL.value,
+      (_, _) => writesL,
       owritesR,
       typeTag)
 }
@@ -77,7 +77,7 @@ trait DerivedOWritesInstances1 extends DerivedOWritesInstances2 {
     typeTag: TT[FieldType[K, L]]
   ): DerivedOWrites[FieldType[K, L] :+: R, TT] =
     DerivedOWritesUtil.makeCoProductOWrites(
-      owritesL.value.owrites,
+      (tagOwrites, adapter) => owritesL.map(_.owrites(tagOwrites, adapter)),
       owritesR,
       typeTag)
 }
@@ -116,7 +116,7 @@ trait DerivedOWritesInstances3 {
 
 private[derived] object DerivedOWritesUtil {
   def makeCoProductOWrites[K <: Symbol, L, R <: Coproduct, TT[A] <: TypeTag[A]](
-    makeWritesL: (TypeTagOWrites, NameAdapter) => Writes[L],
+    makeWritesL: (TypeTagOWrites, NameAdapter) => Lazy[Writes[L]],
     owritesR: Lazy[DerivedOWrites[R, TT]],
     typeTag: TT[FieldType[K, L]]
   ): DerivedOWrites[FieldType[K, L] :+: R, TT] =
@@ -127,7 +127,7 @@ private[derived] object DerivedOWritesUtil {
         val derivedOwriteR = owritesR.value.owrites(tagOwrites, adapter)
 
         OWrites[FieldType[K, L] :+: R] {
-          case Inl(l) => tagOwrites.owrites(typeTag.value, writesL).writes(l)
+          case Inl(l) => tagOwrites.owrites(typeTag.value, writesL.value).writes(l)
           case Inr(r) => derivedOwriteR.writes(r)
         }
       }
diff --git a/library/src/main/scala/julienrf/json/derived/typetags.scala b/library/src/main/scala/julienrf/json/derived/typetags.scala
index 3a6c17e..68b6b9e 100644
--- a/library/src/main/scala/julienrf/json/derived/typetags.scala
+++ b/library/src/main/scala/julienrf/json/derived/typetags.scala
@@ -139,7 +139,6 @@ object TypeTagReads {
     *
     * @param tagReads A way to decode the type tag value.
     */
-  //TODO docs on edge case
   def flat(tagReads: Reads[String]): TypeTagReads =
     new TypeTagReads {
       def reads[A](typeName: String, reads: Reads[A]): Reads[A] = {
diff --git a/library/src/test/scala/julienrf/json/derived/DerivedOFormatSuite.scala b/library/src/test/scala/julienrf/json/derived/DerivedOFormatSuite.scala
index 6b90b8f..1abc12d 100644
--- a/library/src/test/scala/julienrf/json/derived/DerivedOFormatSuite.scala
+++ b/library/src/test/scala/julienrf/json/derived/DerivedOFormatSuite.scala
@@ -269,5 +269,61 @@ class DerivedOFormatSuite extends AnyFeatureSpec with Checkers {
       assert(json == Json.obj("type" -> "Bar", "__syntheticWrap__" -> JsNumber(42)))
       assert(fooFormat.reads(json).asEither == Right(foo))
     }
+
+    import TestHelpers._
+    val adt = Z(X(1), Y("VVV"))
+
+    Scenario("supports user-defined recursive formats - nested") {
+      val adtFormat: Format[ADTBase] = {
+        implicit val f1: Format[X] = Json.format
+        implicit val f2: Format[Y] = Json.format
+        implicit lazy val f3: Format[Z] = Json.format
+
+        implicit lazy val f4: Format[ADTBase] = oformat[ADTBase]()
+
+        f4
+      }
+
+      val json = adtFormat.writes(adt)
+      val obj = Json.obj(
+        "Z" -> Json.obj(
+          "l" -> Json.obj("X" -> Json.obj("a" -> 1)),
+          "r" -> Json.obj("Y" -> Json.obj("b" -> "VVV"))))
+
+      assert(json == obj)
+      assert(adtFormat.reads(json).asEither == Right(adt))
+    }
+
+    Scenario("supports user-defined recursive formats - flat") {
+      val adtFormat: Format[ADTBase] = {
+        implicit val f1: Format[X] = Json.format
+        implicit val f2: Format[Y] = Json.format
+        implicit lazy val f3: Format[Z] = Json.format
+
+        implicit lazy val f4: Format[ADTBase] = flat.oformat((__ \ "type").format[String])
+
+        f4
+      }
+
+      val json = adtFormat.writes(adt)
+      val obj = Json.obj(
+        "type" -> "Z",
+        "l" -> Json.obj("type" -> "X", "a" -> 1),
+        "r" -> Json.obj("type" -> "Y", "b" -> "VVV"))
+
+      assert(json == obj)
+      assert(adtFormat.reads(json).asEither == Right(adt))
+    }
   }
 }
+
+
+object TestHelpers {
+  // Placing it here in a separate object since otherwise the Json.format macro fails to compile
+  // for these types
+  sealed trait ADTBase
+
+  case class X(a: Int) extends ADTBase
+  case class Y(b: String) extends ADTBase
+  case class Z(l: ADTBase, r: ADTBase) extends ADTBase
+}