diff --git a/canopen/objectdictionary/__init__.py b/canopen/objectdictionary/__init__.py
index 09fe6e03..c67b3b4a 100644
--- a/canopen/objectdictionary/__init__.py
+++ b/canopen/objectdictionary/__init__.py
@@ -419,6 +419,12 @@ def add_bit_definition(self, name: str, bits: List[int]) -> None:
         """
         self.bit_definitions[name] = bits
 
+    @property
+    def fixed_size(self) -> bool:
+        """Indicate whether the amount of needed data is known in advance."""
+        # Only for types which we parse using a structure.
+        return self.data_type in self.STRUCT_TYPES
+
     def decode_raw(self, data: bytes) -> Union[int, float, str, bytes, bytearray]:
         if self.data_type == VISIBLE_STRING:
             # Strip any trailing NUL characters from C-based systems
diff --git a/canopen/sdo/client.py b/canopen/sdo/client.py
index 6d92588e..fd5fd99b 100644
--- a/canopen/sdo/client.py
+++ b/canopen/sdo/client.py
@@ -126,9 +126,7 @@ def upload(self, index: int, subindex: int) -> bytes:
         var = self.od.get_variable(index, subindex)
         if var is not None:
             # Found a matching variable in OD
-            # If this is a data type (string, domain etc) the size is
-            # unknown anyway so keep the data as is
-            if var.data_type not in objectdictionary.DATA_TYPES:
+            if var.fixed_size:
                 # Get the size in bytes for this variable
                 var_size = len(var) // 8
                 if response_size is None or var_size < response_size:
diff --git a/test/test_sdo.py b/test/test_sdo.py
index fea52b6a..78012a30 100644
--- a/test/test_sdo.py
+++ b/test/test_sdo.py
@@ -814,7 +814,6 @@ def test_unknown_od_112(self):
 
     def test_unknown_datatype32(self):
         """Test an unknown datatype, but known OD, of 32 bits (4 bytes)."""
-        return  # FIXME: Disabled temporarily until datatype conditionals are fixed, see #436
         # Add fake entry 0x2100 to OD, using fake datatype 0xFF
         if 0x2100 not in self.node.object_dictionary:
             fake_var = ODVariable("Fake", 0x2100)
@@ -829,7 +828,6 @@ def test_unknown_datatype32(self):
 
     def test_unknown_datatype112(self):
         """Test an unknown datatype, but known OD, of 112 bits (14 bytes)."""
-        return  # FIXME: Disabled temporarily until datatype conditionals are fixed, see #436
         # Add fake entry 0x2100 to OD, using fake datatype 0xFF
         if 0x2100 not in self.node.object_dictionary:
             fake_var = ODVariable("Fake", 0x2100)