diff --git a/bitsharesbase/operations.py b/bitsharesbase/operations.py
index f18552d..89a62dd 100644
--- a/bitsharesbase/operations.py
+++ b/bitsharesbase/operations.py
@@ -1278,14 +1278,22 @@ def __init__(self, *args, **kwargs):
         else:
             if len(args) == 1 and len(kwargs) == 0:
                 kwargs = args[0]
+            if "new_fee_rate" in kwargs:
+                new_fee_rate = Optional(Uint32(kwargs["new_fee_rate"]))
+            else:
+                new_fee_rate = Optional(None)
+            if "delta_amount" in kwargs:
+                delta_amount = Optional(Asset(kwargs["delta_amount"]))
+            else:
+                delta_amount = Optional(None)
             super().__init__(
                 OrderedDict(
                     [
                         ("fee", Asset(kwargs["fee"])),
                         ("owner_account", ObjectId(kwargs["owner_account"], "account")),
                         ("fund_id", ObjectId(kwargs["fund_id"], "samet_fund")),
-                        ("delta_amount", Optional(Asset(kwargs["delta_amount"]))),
-                        ("new_fee_rate", Optional(Uint32(kwargs["new_fee_rate"]))),
+                        ("delta_amount", delta_amount),
+                        ("new_fee_rate", new_fee_rate),
                         ("extensions", Set([])),
                     ]
                 )
@@ -1405,46 +1413,68 @@ def __init__(self, *args, **kwargs):
         else:
             if len(args) == 1 and len(kwargs) == 0:
                 kwargs = args[0]
+            if kwargs.get("min_deal_amount"):
+                min_deal_amount = Optional(Int64(kwargs["min_deal_amount"]))
+            else:
+                min_deal_amount = Optional(None)
+            if kwargs.get("enabled"):
+                enabled = Optional(Bool(kwargs["enabled"]))
+            else:
+                enabled = Optional(None)
+            if kwargs.get("auto_disable_time"):
+                auto_disable_time = Optional(PointInTime(kwargs["auto_disable_time"]))
+            else:
+                auto_disable_time = Optional(None)
+            if kwargs.get("acceptable_collateral"):
+                acceptable_collateral = Optional(
+                    Map(
+                        [
+                            [ObjectId(k[0], "asset"), Price(k[1])]
+                            for k in kwargs["acceptable_collateral"]
+                        ]
+                    )
+                )
+            else:
+                acceptable_collateral = Optional(None)
+            if kwargs.get("acceptable_borrowers"):
+                acceptable_borrowers = Optional(
+                    Map(
+                        [
+                            [ObjectId(k[0], "account"), Int64(k[1])]
+                            for k in kwargs["acceptable_borrowers"]
+                        ]
+                    )
+                )
+            else:
+                acceptable_borrowers = Optional(None)
+            if kwargs.get("max_duration_seconds"):
+                max_duration_seconds = Optional(
+                    Uint32(kwargs.get("max_duration_seconds"))
+                )
+            else:
+                max_duration_seconds = Optional(None)
+            if kwargs.get("fee_rate"):
+                fee_rate = Optional(Uint32(kwargs.get("fee_rate")))
+            else:
+                fee_rate = Optional(None)
+            if kwargs.get("delta_amount"):
+                delta_amount = Optional(Asset(kwargs.get("delta_amount")))
+            else:
+                delta_amount = Optional(None)
             super().__init__(
                 OrderedDict(
                     [
                         ("fee", Asset(kwargs["fee"])),
                         ("owner_account", ObjectId(kwargs["owner_account"], "account")),
                         ("offer_id", ObjectId(kwargs["offer_id"], "credit_offer")),
-                        ("delta_amount", Optional(Asset(kwargs["fee"]))),
-                        ("fee_rate", Optional(Uint32(kwargs["fee_rate"]))),
-                        (
-                            "max_duration_seconds",
-                            Optional(Uint32(kwargs["max_duration_seconds"])),
-                        ),
-                        ("min_deal_amount", Optional(Int64(kwargs["min_deal_amount"]))),
-                        ("enabled", Optional(Bool(kwargs["enabled"]))),
-                        (
-                            "auto_disable_time",
-                            Optional(PointInTime(kwargs["auto_disable_time"])),
-                        ),
-                        (
-                            "acceptable_collateral",
-                            Optional(
-                                Map(
-                                    [
-                                        [ObjectId(k[0], "asset"), Price(k[1])]
-                                        for k in kwargs["acceptable_collateral"]
-                                    ]
-                                )
-                            ),
-                        ),
-                        (
-                            "acceptable_borrowers",
-                            Optional(
-                                Map(
-                                    [
-                                        [ObjectId(k[0], "account"), Int64(k[1])]
-                                        for k in kwargs["acceptable_borrowers"]
-                                    ]
-                                )
-                            ),
-                        ),
+                        ("delta_amount", delta_amount),
+                        ("fee_rate", fee_rate),
+                        ("max_duration_seconds", max_duration_seconds),
+                        ("min_deal_amount", min_deal_amount),
+                        ("enabled", enabled),
+                        ("auto_disable_time", auto_disable_time),
+                        ("acceptable_collateral", acceptable_collateral),
+                        ("acceptable_borrowers", acceptable_borrowers),
                         ("extensions", Set([])),
                     ]
                 )
diff --git a/tests/test_transactions.py b/tests/test_transactions.py
index 6820f93..028ec4f 100644
--- a/tests/test_transactions.py
+++ b/tests/test_transactions.py
@@ -1232,13 +1232,13 @@ def test_credit_offer_update(self):
             }
         )
         self.cm = (
-            "f68585abf4dce7c8045701470000000000000000007b010100"
+            "f68585abf4dce7c8045701470000000000000000007b010101"
             "0000000000000000010100000001e8030000010a0000000000"
             "0000010101800092650101d52b01000000000000000090d003"
-            "0000000000d52b010164e8030000000000000000012064575b"
-            "5fd2347411a643c54a2aaf2550c0c5653334ec81ca28a1e68f"
-            "fd7e7fd07748121135e01947ae317e3b7ae9263149b96e9630"
-            "1b16571984b94f7c72ebd9"
+            "0000000000d52b010164e8030000000000000000011f08187d"
+            "ea87e4306cb8e6fc9ddeeb38053499a86f5c01d8bfa8b72257"
+            "564bd3250bd4868d5db692077526b901a019cb8e2049e5daf7"
+            "95a7ba17e6122fdb0fb20a"
         )
         self.doit(1)