diff --git a/zio-schema-msg-pack/src/main/scala/zio/schema/codec/MessagePackDecoder.scala b/zio-schema-msg-pack/src/main/scala/zio/schema/codec/MessagePackDecoder.scala
index cad77533f..eaf9786aa 100644
--- a/zio-schema-msg-pack/src/main/scala/zio/schema/codec/MessagePackDecoder.scala
+++ b/zio-schema-msg-pack/src/main/scala/zio/schema/codec/MessagePackDecoder.scala
@@ -405,32 +405,32 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass9Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, Z](path: Path, schema: Schema.CaseClass9[A1, A2, A3, A4, A5, A6, A7, A8, A9, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9)
     } yield schema.construct(buffer(0).asInstanceOf[A1], buffer(1).asInstanceOf[A2], buffer(2).asInstanceOf[A3], buffer(3).asInstanceOf[A4], buffer(4).asInstanceOf[A5], buffer(5).asInstanceOf[A6], buffer(6).asInstanceOf[A7], buffer(7).asInstanceOf[A8], buffer(8).asInstanceOf[A9])
 
   private def caseClass10Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Z](path: Path, schema: Schema.CaseClass10[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10)
     } yield schema.construct(buffer(0).asInstanceOf[A1], buffer(1).asInstanceOf[A2], buffer(2).asInstanceOf[A3], buffer(3).asInstanceOf[A4], buffer(4).asInstanceOf[A5], buffer(5).asInstanceOf[A6], buffer(6).asInstanceOf[A7], buffer(7).asInstanceOf[A8], buffer(8).asInstanceOf[A9], buffer(9).asInstanceOf[A10])
 
   private def caseClass11Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, Z](path: Path, schema: Schema.CaseClass11[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11)
     } yield schema.construct(buffer(0).asInstanceOf[A1], buffer(1).asInstanceOf[A2], buffer(2).asInstanceOf[A3], buffer(3).asInstanceOf[A4], buffer(4).asInstanceOf[A5], buffer(5).asInstanceOf[A6], buffer(6).asInstanceOf[A7], buffer(7).asInstanceOf[A8], buffer(8).asInstanceOf[A9], buffer(9).asInstanceOf[A10], buffer(10).asInstanceOf[A11])
 
   private def caseClass12Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, Z](path: Path, schema: Schema.CaseClass12[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12)
     } yield schema.construct(buffer(0).asInstanceOf[A1], buffer(1).asInstanceOf[A2], buffer(2).asInstanceOf[A3], buffer(3).asInstanceOf[A4], buffer(4).asInstanceOf[A5], buffer(5).asInstanceOf[A6], buffer(6).asInstanceOf[A7], buffer(7).asInstanceOf[A8], buffer(8).asInstanceOf[A9], buffer(9).asInstanceOf[A10], buffer(10).asInstanceOf[A11], buffer(11).asInstanceOf[A12])
 
   private def caseClass13Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, Z](path: Path, schema: Schema.CaseClass13[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13)
     } yield schema.construct(buffer(0).asInstanceOf[A1], buffer(1).asInstanceOf[A2], buffer(2).asInstanceOf[A3], buffer(3).asInstanceOf[A4], buffer(4).asInstanceOf[A5], buffer(5).asInstanceOf[A6], buffer(6).asInstanceOf[A7], buffer(7).asInstanceOf[A8], buffer(8).asInstanceOf[A9], buffer(9).asInstanceOf[A10], buffer(10).asInstanceOf[A11], buffer(11).asInstanceOf[A12], buffer(12).asInstanceOf[A13])
 
   private def caseClass14Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Z](path: Path, schema: Schema.CaseClass14[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -450,7 +450,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass15Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Z](path: Path, schema: Schema.CaseClass15[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -471,7 +471,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass16Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, Z](path: Path, schema: Schema.CaseClass16[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -493,7 +493,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass17Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, Z](path: Path, schema: Schema.CaseClass17[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -516,7 +516,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass18Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, Z](path: Path, schema: Schema.CaseClass18[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -540,7 +540,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass19Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, Z](path: Path, schema: Schema.CaseClass19[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -565,7 +565,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass20Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, Z](path: Path, schema: Schema.CaseClass20[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -591,7 +591,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass21Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, Z](path: Path, schema: Schema.CaseClass21[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20, schema.field21)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20, schema.field21)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
@@ -618,7 +618,7 @@ private[codec] class MessagePackDecoder(bytes: Chunk[Byte]) {
 
   private def caseClass22Decoder[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, Z](path: Path, schema: Schema.CaseClass22[A1, A2, A3, A4, A5, A6, A7, A8, A9, A10, A11, A12, A13, A14, A15, A16, A17, A18, A19, A20, A21, A22, Z]): Result[Z] =
     for {
-      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field9, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20, schema.field21, schema.field22)
+      buffer <- unsafeDecodeFields(path, schema.field1, schema.field2, schema.field3, schema.field4, schema.field5, schema.field6, schema.field7, schema.field8, schema.field9, schema.field10, schema.field11, schema.field12, schema.field13, schema.field14, schema.field15, schema.field16, schema.field17, schema.field18, schema.field19, schema.field20, schema.field21, schema.field22)
     } yield schema.construct(
       buffer(0).asInstanceOf[A1],
       buffer(1).asInstanceOf[A2],
diff --git a/zio-schema-msg-pack/src/test/scala/zio/schema/codec/MessagePackCodecSpec.scala b/zio-schema-msg-pack/src/test/scala/zio/schema/codec/MessagePackCodecSpec.scala
index 2de452bdd..95bd5378c 100644
--- a/zio-schema-msg-pack/src/test/scala/zio/schema/codec/MessagePackCodecSpec.scala
+++ b/zio-schema-msg-pack/src/test/scala/zio/schema/codec/MessagePackCodecSpec.scala
@@ -135,6 +135,13 @@ object MessagePackCodecSpec extends ZIOSpecDefault {
           ed  <- encodeAndDecodeNS(schemaHighArityRecord, HighArity())
         } yield assert(ed)(equalTo(HighArity())) && assert(e)(equalTo(res))
       },
+      test("case classes with arity 22") {
+        for {
+          e   <- encode(schemaMaxArityCaseClass, MaxArityCaseClass()).map(toHex)
+          res <- write(MaxArityCaseClass())
+          ed  <- encodeAndDecodeNS(schemaMaxArityCaseClass, MaxArityCaseClass())
+        } yield assert(ed)(equalTo(MaxArityCaseClass())) && assert(e)(equalTo(res))
+      },
       test("integer") {
         for {
           ed2 <- encodeAndDecodeNS(schemaBasicInt, BasicInt(150))
@@ -938,6 +945,33 @@ object MessagePackCodecSpec extends ZIOSpecDefault {
     f24: Int = 24
   )
 
+  case class MaxArityCaseClass(
+    f1: Int = 1,
+    f2: Int = 2,
+    f3: Int = 3,
+    f4: Int = 4,
+    f5: Int = 5,
+    f6: Int = 6,
+    f7: Int = 7,
+    f8: Int = 8,
+    f9: Int = 9,
+    f10: Int = 10,
+    f11: Int = 11,
+    f12: Int = 12,
+    f13: Int = 13,
+    f14: Int = 14,
+    f15: Int = 15,
+    f16: Int = 16,
+    f17: Int = 17,
+    f18: Int = 18,
+    f19: Int = 19,
+    f20: Int = 20,
+    f21: Int = 21,
+    f22: Int = 22
+  )
+
+  lazy val schemaMaxArityCaseClass: Schema[MaxArityCaseClass] = DeriveSchema.gen[MaxArityCaseClass]
+
   lazy val schemaHighArityRecord: Schema[HighArity] = DeriveSchema.gen[HighArity]
 
   lazy val schemaOneOf: Schema[OneOf] = DeriveSchema.gen[OneOf]