diff --git a/.gitignore b/.gitignore
index 1ca16fe5a..1984386e6 100644
--- a/.gitignore
+++ b/.gitignore
@@ -212,6 +212,7 @@ TAGS
 /tests/conform/test-conformance-result.xml
 /tests/conform/test-fixed-size
 /tests/conform/test-preferred-size
+/tests/conform/test-units-cache
 /tests/micro-bench/test-text-perf
 /tests/micro-bench/test-text
 /tests/micro-bench/test-picking
diff --git a/clutter/clutter-backend.c b/clutter/clutter-backend.c
index c95ac9bc7..96b22213f 100644
--- a/clutter/clutter-backend.c
+++ b/clutter/clutter-backend.c
@@ -63,6 +63,7 @@ struct _ClutterBackendPrivate
   gdouble resolution;
 
   gfloat units_per_em;
+  gint32 units_serial;
 
   cairo_font_options_t *font_options;
 
@@ -160,7 +161,10 @@ get_units_per_em (ClutterBackend       *backend,
 static void
 clutter_backend_real_resolution_changed (ClutterBackend *backend)
 {
-  backend->priv->units_per_em = get_units_per_em (backend, NULL);
+  ClutterBackendPrivate *priv = backend->priv;
+
+  priv->units_per_em = get_units_per_em (backend, NULL);
+  priv->units_serial += 1;
 
   CLUTTER_NOTE (BACKEND, "Units per em: %.2f", backend->priv->units_per_em);
 }
@@ -168,7 +172,10 @@ clutter_backend_real_resolution_changed (ClutterBackend *backend)
 static void
 clutter_backend_real_font_changed (ClutterBackend *backend)
 {
-  backend->priv->units_per_em = get_units_per_em (backend, NULL);
+  ClutterBackendPrivate *priv = backend->priv;
+
+  priv->units_per_em = get_units_per_em (backend, NULL);
+  priv->units_serial += 1;
 
   CLUTTER_NOTE (BACKEND, "Units per em: %.2f", backend->priv->units_per_em);
 }
@@ -212,7 +219,9 @@ clutter_backend_init (ClutterBackend *backend)
   priv = backend->priv = CLUTTER_BACKEND_GET_PRIVATE (backend);
 
   priv->resolution = -1.0;
+
   priv->units_per_em = -1.0;
+  priv->units_serial = 1;
 }
 
 void
@@ -721,3 +730,11 @@ clutter_backend_get_font_name (ClutterBackend *backend)
 
   return priv->font_name;
 }
+
+gint32
+_clutter_backend_get_units_serial (ClutterBackend *backend)
+{
+  g_return_val_if_fail (CLUTTER_IS_BACKEND (backend), 0);
+
+  return backend->priv->units_serial;
+}
diff --git a/clutter/clutter-private.h b/clutter/clutter-private.h
index bd6f5dbe2..57ec0481d 100644
--- a/clutter/clutter-private.h
+++ b/clutter/clutter-private.h
@@ -255,6 +255,8 @@ void _clutter_actor_set_enable_paint_unmapped (ClutterActor *self,
 
 void _clutter_run_repaint_functions (void);
 
+gint32 _clutter_backend_get_units_serial (ClutterBackend *backend);
+
 G_END_DECLS
 
 #endif /* _HAVE_CLUTTER_PRIVATE_H */
diff --git a/clutter/clutter-units.c b/clutter/clutter-units.c
index 595f0a50f..4831fd17d 100644
--- a/clutter/clutter-units.c
+++ b/clutter/clutter-units.c
@@ -150,12 +150,17 @@ void
 clutter_units_from_mm (ClutterUnits *units,
                        gfloat        mm)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_MM;
   units->value      = mm;
   units->pixels     = units_mm_to_pixels (mm);
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -171,12 +176,17 @@ void
 clutter_units_from_cm (ClutterUnits *units,
                        gfloat        cm)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_CM;
   units->value      = cm;
   units->pixels     = units_cm_to_pixels (cm);
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -192,12 +202,17 @@ void
 clutter_units_from_pt (ClutterUnits *units,
                        gfloat        pt)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_POINT;
   units->value      = pt;
   units->pixels     = units_pt_to_pixels (pt);
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -214,12 +229,17 @@ void
 clutter_units_from_em (ClutterUnits *units,
                        gfloat        em)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_EM;
   units->value      = em;
   units->pixels     = units_em_to_pixels (NULL, em);
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -237,12 +257,17 @@ clutter_units_from_em_for_font (ClutterUnits *units,
                                 const gchar  *font_name,
                                 gfloat        em)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_EM;
   units->value      = em;
   units->pixels     = units_em_to_pixels (font_name, em);
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -258,12 +283,17 @@ void
 clutter_units_from_pixels (ClutterUnits *units,
                            gint          px)
 {
+  ClutterBackend *backend;
+
   g_return_if_fail (units != NULL);
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type  = CLUTTER_UNIT_PIXEL;
   units->value      = px;
   units->pixels     = px;
   units->pixels_set = TRUE;
+  units->serial     = _clutter_backend_get_units_serial (backend);
 }
 
 /**
@@ -353,8 +383,18 @@ clutter_units_free (ClutterUnits *units)
 gfloat
 clutter_units_to_pixels (ClutterUnits *units)
 {
+  ClutterBackend *backend;
+
   g_return_val_if_fail (units != NULL, 0.0);
 
+  /* if the backend settings changed we evict the cached value */
+  backend = clutter_get_default_backend ();
+  if (units->serial != _clutter_backend_get_units_serial (backend))
+    units->pixels_set = FALSE;
+
+  if (units->pixels_set)
+    return units->pixels;
+
   switch (units->unit_type)
     {
     case CLUTTER_UNIT_MM:
@@ -379,6 +419,7 @@ clutter_units_to_pixels (ClutterUnits *units)
     }
 
   units->pixels_set = TRUE;
+  units->serial = _clutter_backend_get_units_serial (backend);
 
   return units->pixels;
 }
@@ -431,6 +472,7 @@ gboolean
 clutter_units_from_string (ClutterUnits *units,
                            const gchar  *str)
 {
+  ClutterBackend *backend;
   ClutterUnitType unit_type;
   gfloat value;
 
@@ -503,9 +545,12 @@ clutter_units_from_string (ClutterUnits *units,
   if (*str != '\0')
     return FALSE;
 
+  backend = clutter_get_default_backend ();
+
   units->unit_type = unit_type;
   units->value = value;
   units->pixels_set = FALSE;
+  units->serial = _clutter_backend_get_units_serial (backend);
 
   return TRUE;
 }
diff --git a/clutter/clutter-units.h b/clutter/clutter-units.h
index e67af95ae..a770d1fec 100644
--- a/clutter/clutter-units.h
+++ b/clutter/clutter-units.h
@@ -77,11 +77,18 @@ struct _ClutterUnits
   gfloat value;
 
   /* pre-filled by the provided constructors */
+
+  /* cached pixel value */
   gfloat pixels;
+
+  /* whether the :pixels field is set */
   guint pixels_set;
 
+  /* the serial coming from the backend, used to evict the cache */
+  gint32 serial;
+
   /* padding for eventual expansion */
-  gint64 __padding_1;
+  gint32 __padding_1;
   gint64 __padding_2;
 };
 
diff --git a/tests/conform/test-clutter-units.c b/tests/conform/test-clutter-units.c
index a685d1ad7..105c454a9 100644
--- a/tests/conform/test-clutter-units.c
+++ b/tests/conform/test-clutter-units.c
@@ -3,6 +3,29 @@
 
 #include "test-conform-common.h"
 
+void
+test_units_cache (TestConformSimpleFixture *fixture,
+                  gconstpointer data)
+{
+  ClutterUnits units;
+  ClutterBackend *backend;
+  gfloat pixels;
+  gdouble dpi;
+
+  backend = clutter_get_default_backend ();
+
+  dpi = clutter_backend_get_resolution (backend);
+
+  clutter_units_from_em (&units, 1.0);
+  pixels = clutter_units_to_pixels (&units);
+
+  clutter_backend_set_resolution (backend, dpi + 10);
+  g_assert_cmpfloat (clutter_units_to_pixels (&units), !=, pixels);
+
+  clutter_backend_set_resolution (backend, dpi);
+  g_assert_cmpfloat (clutter_units_to_pixels (&units), ==, pixels);
+}
+
 void
 test_units_constructors (TestConformSimpleFixture *fixture,
                          gconstpointer data)
diff --git a/tests/conform/test-conform-main.c b/tests/conform/test-conform-main.c
index d8d4b1c42..2b2624434 100644
--- a/tests/conform/test-conform-main.c
+++ b/tests/conform/test-conform-main.c
@@ -167,6 +167,7 @@ main (int argc, char **argv)
 
   TEST_CONFORM_SIMPLE ("/units", test_units_constructors);
   TEST_CONFORM_SIMPLE ("/units", test_units_string);
+  TEST_CONFORM_SIMPLE ("/units", test_units_cache);
 
   TEST_CONFORM_SIMPLE ("/group", test_group_depth_sorting);