diff --git a/c_gen/build_of_g.py b/c_gen/build_of_g.py
index f117bfd..85be353 100755
--- a/c_gen/build_of_g.py
+++ b/c_gen/build_of_g.py
@@ -153,6 +153,11 @@
             # but is variable length
             bytes = -1
             len_update = 8
+        elif base_type == "of_oxm_header_t":
+            # This is a special case: it has non-zero min length
+            # but is variable length
+            bytes = -1
+            len_update = 4
         elif base_type in of_g.of_base_types:
             bytes = of_g.of_base_types[base_type]["bytes"]
         else:
@@ -330,7 +335,7 @@
                 else:
                     # HACK the C backend does not yet support of_oxm_t
                     if m.oftype == 'of_oxm_t':
-                        m_type = 'of_octets_t'
+                        m_type = 'of_oxm_header_t'
                     else:
                         enum = find(lambda e: e.name == m.oftype, protocol.enums)
                         if enum and "wire_type" in enum.params: