diff --git a/gusto/equations.py b/gusto/equations.py
index b6001ad9b..e8d51a9aa 100644
--- a/gusto/equations.py
+++ b/gusto/equations.py
@@ -10,7 +10,7 @@
 from gusto.fml.form_manipulation_labelling import Term, all_terms, keep, drop, Label
 from gusto.labels import (subject, time_derivative, transport, prognostic,
                           transporting_velocity, replace_subject, linearisation,
-                          name, pressure_gradient, coriolis,
+                          name, pressure_gradient, coriolis, perp,
                           replace_trial_function, hydrostatic)
 from gusto.thermodynamics import exner_pressure
 from gusto.transport_forms import (advection_form, continuity_form,
@@ -663,12 +663,17 @@ def __init__(self, domain, parameters, fexpr=None, bexpr=None,
         if fexpr is not None:
             V = FunctionSpace(domain.mesh, "CG", 1)
             f = self.prescribed_fields("coriolis", V).interpolate(fexpr)
-            coriolis_form = coriolis(
-                subject(prognostic(f*inner(domain.perp(u), w)*dx, "u"), self.X))
+            coriolis_form = perp(
+                coriolis(
+                    subject(prognostic(f*inner(u, w)*dx, "u"), self.X)
+                ), domain.perp)
             # Add linearisation
-            linear_coriolis = coriolis(
-                subject(prognostic(f*inner(domain.perp(u_trial), w)*dx, "u"), self.X))
-            coriolis_form = linearisation(coriolis_form, linear_coriolis)
+            if self.linearisation_map(coriolis_form.terms[0]):
+                linear_coriolis = perp(
+                    coriolis(
+                        subject(prognostic(f*inner(u_trial, w)*dx, "u"), self.X)
+                    ), domain.perp)
+                coriolis_form = linearisation(coriolis_form, linear_coriolis)
             residual += coriolis_form
 
         if bexpr is not None:
diff --git a/gusto/labels.py b/gusto/labels.py
index 23fd2d1a7..2f17bc6a4 100644
--- a/gusto/labels.py
+++ b/gusto/labels.py
@@ -4,7 +4,7 @@
 from firedrake import Function, split, MixedElement
 from gusto.configuration import IntegrateByParts, TransportEquationType
 from gusto.fml.form_manipulation_labelling import Term, Label, LabelledForm
-from types import MethodType
+from types import MethodType, LambdaType
 
 
 def replace_test_function(new_test):
@@ -164,6 +164,13 @@ def repl(t):
 
         new_form = ufl.replace(t.form, replace_dict)
 
+        # this is necessary to defer applying the perp until after the
+        # subject is replaced because otherwise replace cannot find
+        # the subject
+        if t.has_label(perp):
+            perp_function = t.get(perp)
+            new_form = ufl.replace(new_form, {split(new)[0]: perp_function(split(new)[0])})
+
         return Term(new_form, t.labels)
 
     return repl
@@ -186,3 +193,4 @@ def repl(t):
 name = Label("name", validator=lambda value: type(value) == str)
 ibp_label = Label("ibp", validator=lambda value: type(value) == IntegrateByParts)
 hydrostatic = Label("hydrostatic", validator=lambda value: type(value) in [LabelledForm, Term])
+perp = Label("perp", validator=lambda value: isinstance(value, LambdaType))