diff --git a/serialization/object_serialization.nim b/serialization/object_serialization.nim
index 2e6ebe7..e6ecc4c 100644
--- a/serialization/object_serialization.nim
+++ b/serialization/object_serialization.nim
@@ -101,6 +101,7 @@ macro enumAllSerializedFieldsImpl(T: type, body: untyped): untyped =
 
     let
       fieldType = field.typ
+      FieldTypeSym = getTypeInst(fieldType)
       fieldIdent = field.name
       realFieldName = newLit($fieldIdent.skipPragma)
       serializedFieldName = field.readPragma("serializedFieldName")
@@ -132,14 +133,15 @@ macro enumAllSerializedFieldsImpl(T: type, body: untyped): untyped =
     result.add quote do:
       block:
         when compiles(type(`field`)):
-          `fieldNameDefs`
-
           type FieldType {.inject, used.} = type(`field`)
 
-          template fieldCaseDiscriminator: auto {.used.} = `discriminator`
-          template fieldCaseBranches: auto {.used.} = `branches`
+          when FieldType is `FieldTypeSym`:
+            `fieldNameDefs`
 
-          `body`
+            template fieldCaseDiscriminator: auto {.used.} = `discriminator`
+            template fieldCaseBranches: auto {.used.} = `branches`
+
+            `body`
 
     i += 1
 
diff --git a/tests/test_object_serialization.nim b/tests/test_object_serialization.nim
index 1ca35cd..c0a2586 100644
--- a/tests/test_object_serialization.nim
+++ b/tests/test_object_serialization.nim
@@ -4,19 +4,41 @@ import
   ../serialization/object_serialization,
   ../serialization/testing/generic_suite
 
+type
+  Untrusted = object
+  Trusted = object
+
+  Signature = object
+    p: int
+    k: float
+
+  TrustedSignature = object
+    data: string
+
+  SignatureHolder[TrustLevel] = object
+    when TrustLevel is Trusted:
+      sig: TrustedSignature
+      origin: string
+    else:
+      sig: Signature
+
+func collectFields(T: type): seq[string] =
+  enumAllSerializedFields(T):
+    result.add(name(FieldType) & " " & fieldName & fieldCaseDiscriminator)
+
 suite "object serialization":
-  setup:
-    var fieldsList = newSeq[string]()
-
   test "custom fields order":
-    enumAllSerializedFields(Simple):
-      fieldsList.add(name(FieldType) & " " & fieldName & fieldCaseDiscriminator)
-
-    check fieldsList == @["Meter distance", "int x", "string y"]
+    check collectFields(Simple) == @["Meter distance", "int x", "string y"]
 
   test "tuples handling":
+    var fieldsList = newSeq[string]()
+
     enumAllSerializedFields(HoldsTuples):
       fieldsList.add(fieldName & ": " & $isTuple(FieldType))
 
     check fieldsList == @["t1: true", "t2: true", "t3: true"]
 
+  test "when statements":
+    check collectFields(SignatureHolder[Trusted]) == @["TrustedSignature sig", "string origin"]
+    check collectFields(SignatureHolder[Untrusted]) == @["Signature sig"]
+