diff --git a/CHANGELOG-unreleased.md b/CHANGELOG-unreleased.md
index 2bf17f470..cb79874b1 100644
--- a/CHANGELOG-unreleased.md
+++ b/CHANGELOG-unreleased.md
@@ -31,5 +31,6 @@ the released changes.
 - fixed docstring for `add_param_from_top`
 - Gridded calculations now respect logger settings
 - Event TOAs now have default error that is non-zero, and can set as desired
+- Model conversion ICRS <-> ECL works if PM uncertainties are not set
 - Fix `merge_TOAs()` to allow lists of length 1
 ### Removed
\ No newline at end of file
diff --git a/src/pint/models/astrometry.py b/src/pint/models/astrometry.py
index 6f0af367e..38b5ac7c6 100644
--- a/src/pint/models/astrometry.py
+++ b/src/pint/models/astrometry.py
@@ -957,8 +957,12 @@ def as_ECL(self, epoch=None, ecl="IERS2010"):
             lat=self.ELAT.quantity,
             obliquity=OBL[self.ECL.value],
             obstime=self.POSEPOCH.quantity,
-            pm_lon_coslat=self.PMELONG.uncertainty,
-            pm_lat=self.PMELAT.uncertainty,
+            pm_lon_coslat=self.PMELONG.uncertainty
+            if self.PMELONG.uncertainty is not None
+            else 0 * self.PMELONG.units,
+            pm_lat=self.PMELAT.uncertainty
+            if self.PMELAT.uncertainty is not None
+            else 0 * self.PMELAT.units,
             frame=PulsarEcliptic,
         )
         c_ECL = c.transform_to(PulsarEcliptic(ecl=ecl))
@@ -1007,8 +1011,12 @@ def as_ICRS(self, epoch=None):
             lat=self.ELAT.quantity,
             obliquity=OBL[self.ECL.value],
             obstime=self.POSEPOCH.quantity,
-            pm_lon_coslat=self.ELONG.uncertainty * np.cos(self.ELAT.quantity) / dt,
-            pm_lat=self.ELAT.uncertainty / dt,
+            pm_lon_coslat=self.ELONG.uncertainty * np.cos(self.ELAT.quantity) / dt
+            if self.ELONG.uncertainty is not None
+            else 0 * self.ELONG.units / dt,
+            pm_lat=self.ELAT.uncertainty / dt
+            if self.ELAT.uncertainty is not None
+            else 0 * self.ELAT.units / dt,
             frame=PulsarEcliptic,
         )
         c_ICRS = c.transform_to(coords.ICRS)
@@ -1021,8 +1029,12 @@ def as_ICRS(self, epoch=None):
             lat=self.ELAT.quantity,
             obliquity=OBL[self.ECL.value],
             obstime=self.POSEPOCH.quantity,
-            pm_lon_coslat=self.PMELONG.uncertainty,
-            pm_lat=self.PMELAT.uncertainty,
+            pm_lon_coslat=self.PMELONG.uncertainty
+            if self.PMELONG.uncertainty is not None
+            else 0 * self.PMELONG.units,
+            pm_lat=self.PMELAT.uncertainty
+            if self.PMELAT.uncertainty is not None
+            else 0 * self.PMELAT.units,
             frame=PulsarEcliptic,
         )
         c_ICRS = c.transform_to(coords.ICRS)
diff --git a/tests/test_modelconversions.py b/tests/test_modelconversions.py
index 4cd4ad3e1..dddae8d9c 100644
--- a/tests/test_modelconversions.py
+++ b/tests/test_modelconversions.py
@@ -70,6 +70,37 @@ def test_ECL_to_ICRS():
     assert np.allclose(r_ECL.resids, r_ICRS.resids)
 
 
+def test_ICRS_to_ECL_nouncertainties():
+    # start with ICRS model with no pm uncertainties, get residuals with ECL model, compare
+    model_ICRS = get_model(io.StringIO(modelstring_ICRS))
+    for p in ["PMRA", "PMDEC"]:
+        getattr(model_ICRS, p).frozen = True
+        getattr(model_ICRS, p).uncertainties = None
+
+    toas = pint.simulation.make_fake_toas_uniform(
+        MJDStart, MJDStop, NTOA, model=model_ICRS, error=1 * u.us, add_noise=True
+    )
+    r_ICRS = pint.residuals.Residuals(toas, model_ICRS)
+    r_ECL = pint.residuals.Residuals(toas, model_ICRS.as_ECL())
+    assert np.allclose(r_ECL.resids, r_ICRS.resids)
+    # assert model_ICRS.as_ECL(ecl).ECL.value == ecl
+
+
+def test_ECL_to_ICRS_nouncertainties():
+    # start with ECL model with no pm uncertainties, get residuals with ICRS model, compare
+    model_ECL = get_model(io.StringIO(modelstring_ECL))
+    for p in ["PMELONG", "PMELAT"]:
+        getattr(model_ECL, p).frozen = True
+        getattr(model_ECL, p).uncertainties = None
+
+    toas = pint.simulation.make_fake_toas_uniform(
+        MJDStart, MJDStop, NTOA, model=model_ECL, error=1 * u.us, add_noise=True
+    )
+    r_ECL = pint.residuals.Residuals(toas, model_ECL)
+    r_ICRS = pint.residuals.Residuals(toas, model_ECL.as_ICRS())
+    assert np.allclose(r_ECL.resids, r_ICRS.resids)
+
+
 def test_ECL_to_ECL():
     # start with ECL model, get residuals with ECL model with different obliquity, compare
     model_ECL = get_model(io.StringIO(modelstring_ECL))