diff --git a/dascore/viz/spectrogram.py b/dascore/viz/spectrogram.py
index 95293e6b..c62c383a 100644
--- a/dascore/viz/spectrogram.py
+++ b/dascore/viz/spectrogram.py
@@ -84,7 +84,7 @@ def spectrogram(
             spec = _spec.aggregate(other_dim, method="mean").squeeze()
         else:
             raise ValueError(
-                f"The aggr_domain '{aggr_domain}' should be 'time' or 'frequency.'"
+                f"The aggr_domain '{aggr_domain}' should be 'time' or 'frequency'."
             )
     else:
         spec = patch.spectrogram(dim)
diff --git a/tests/test_viz/test_spectrogram.py b/tests/test_viz/test_spectrogram.py
index 27f2a168..8e856abc 100644
--- a/tests/test_viz/test_spectrogram.py
+++ b/tests/test_viz/test_spectrogram.py
@@ -51,7 +51,7 @@ def test_invalid_dim(self, random_patch):
 
     def test_invalid_aggr_domain(self, random_patch):
         """Ensure ValueError is raised for invalid aggr_domain."""
-        with pytest.raises(ValueError, match="should be either 'time' or 'frequency'"):
+        with pytest.raises(ValueError, match="should be 'time' or 'frequency'."):
             random_patch.viz.spectrogram(aggr_domain="invalid")
 
     def test_invalid_patch_dims(self, random_patch):