diff --git a/ethosu/vela/graph_optimiser.py b/ethosu/vela/graph_optimiser.py
index 582924c..3fe703e 100644
--- a/ethosu/vela/graph_optimiser.py
+++ b/ethosu/vela/graph_optimiser.py
@@ -69,6 +69,16 @@
             tens.ops.append(new_op)
         assert tens.shape[axis] == offset
 
+        # If axis = 3, NHCWB16 can only be used in the output if all the concat_start's are a multiple of 16,
+        # as it is only then the address offset for the ofm, for all operations, will be 16 byte aligned
+        # For other values of axis the address offsets will be 16 byte aligned, as they are all based on c = 0
+        # and those addresses are always 16 byte aligned due to the NHCWB16 format.
+        if axis == 3:
+            for op in tens.ops:
+                if op.attrs["concat_start"] % 16 != 0:
+                    tens.avoid_NHCWB16 = True
+                    break
+
     return tens