diff --git a/headers/private/app/MessageBody.h b/headers/private/app/MessageBody.h
index 153458a348..b68143f40f 100644
--- a/headers/private/app/MessageBody.h
+++ b/headers/private/app/MessageBody.h
@@ -125,8 +125,18 @@ status_t BMessageBody::AddData(const char *name, const T1 &data, type_code type)
 	status_t err = B_OK;
 	BMessageField* BMF = FindData(name, type, err);
 
-	// Reset err; we just want the variable
-	err = B_OK;
+	if (err == B_NAME_NOT_FOUND)
+	{
+		// Reset err; we'll create the field
+		err = B_OK;
+	}
+	else
+	{
+		// Looking for B_BAD_TYPE here in particular, which would indicate
+		// that we tried to add data of type X when we already had data of
+		// type Y with the same name
+		return err;
+	}
 
 	if (!BMF)
 	{
@@ -142,7 +152,7 @@ status_t BMessageBody::AddData(const char *name, const T1 &data, type_code type)
 	}
 
 	if (!err)
-	{			
+	{
 		BMessageFieldImpl<T1>* RItem =
 			dynamic_cast<BMessageFieldImpl<T1>*>(BMF);
 		if (!RItem)