-    def __init__(self, family, yaml, req_value, rsp_value):
+    def __init__(self, family, yaml, req_value, rsp_value, default_fixed_header):
         super().__init__(family, yaml)
 
         self.value = req_value if req_value == rsp_value else None

@@ -278,6 +279,7 @@ class SpecOperation(SpecElement):
         self.is_call = 'do' in yaml or 'dump' in yaml
         self.is_async = 'notify' in yaml or 'event' in yaml
         self.is_resv = not self.is_async and not self.is_call
+        self.fixed_header = self.yaml.get('fixed-header', default_fixed_header)
 
         # Added by resolve:
         self.attr_set = None

@@ -384,24 +386,26 @@ class SpecFamily(SpecElement):
     def new_struct(self, elem):
         return SpecStruct(self, elem)
 
-    def new_operation(self, elem, req_val, rsp_val):
-        return SpecOperation(self, elem, req_val, rsp_val)
+    def new_operation(self, elem, req_val, rsp_val, default_fixed_header):
+        return SpecOperation(self, elem, req_val, rsp_val, default_fixed_header)
 
     def add_unresolved(self, elem):
         self._resolution_list.append(elem)
 
     def _dictify_ops_unified(self):
+        default_fixed_header = self.yaml['operations'].get('fixed-header')
         val = 1
         for elem in self.yaml['operations']['list']:
             if 'value' in elem:
                 val = elem['value']
 
-            op = self.new_operation(elem, val, val)
+            op = self.new_operation(elem, val, val, default_fixed_header)
             val += 1
 
             self.msgs[op.name] = op
 
     def _dictify_ops_directional(self):
+        default_fixed_header = self.yaml['operations'].get('fixed-header')
         req_val = rsp_val = 1
         for elem in self.yaml['operations']['list']:
             if 'notify' in elem:

@@ -426,7 +430,7 @@ class SpecFamily(SpecElement):
             else:
                 raise Exception("Can't parse directional ops")
 
-            op = self.new_operation(elem, req_val, rsp_val)
+            op = self.new_operation(elem, req_val, rsp_val, default_fixed_header)