diff --git a/mne/time_frequency/spectrum.py b/mne/time_frequency/spectrum.py
index f7a61e3e57e..167e7eea6d3 100644
--- a/mne/time_frequency/spectrum.py
+++ b/mne/time_frequency/spectrum.py
@@ -1689,12 +1689,12 @@ def combine_spectrum(all_spectrum, weights="nave"):
 
     ch_names = spectrum.ch_names
     for s_ in all_spectrum[1:]:
-        assert s_.ch_names == ch_names, ValueError(
-            f"{spectrum} and {s_} do not contain the same channels"
-        )
-        assert np.max(np.abs(s_.freqs - spectrum.freqs)) < 1e-7, ValueError(
-            f"{spectrum} and {s_} do not contain the same frequencies"
-        )
+        assert (
+            s_.ch_names == ch_names
+        ), f"{spectrum} and {s_} do not contain the same channels"
+        assert (
+            np.max(np.abs(s_.freqs - spectrum.freqs)) < 1e-7
+        ), f"{spectrum} and {s_} do not contain the same frequencies"
 
     # use union of bad channels
     bads = list(
diff --git a/mne/time_frequency/tfr.py b/mne/time_frequency/tfr.py
index 918fea1a33f..b1736f151d2 100644
--- a/mne/time_frequency/tfr.py
+++ b/mne/time_frequency/tfr.py
@@ -3960,12 +3960,12 @@ def combine_tfr(all_tfr, weights="nave"):
 
     ch_names = tfr.ch_names
     for t_ in all_tfr[1:]:
-        assert t_.ch_names == ch_names, ValueError(
-            f"{tfr} and {t_} do not contain the same channels"
-        )
-        assert np.max(np.abs(t_.times - tfr.times)) < 1e-7, ValueError(
-            f"{tfr} and {t_} do not contain the same time instants"
-        )
+        assert (
+            t_.ch_names == ch_names
+        ), f"{tfr} and {t_} do not contain the same channels"
+        assert (
+            np.max(np.abs(t_.times - tfr.times)) < 1e-7
+        ), f"{tfr} and {t_} do not contain the same time instants"
 
     # use union of bad channels
     bads = list(set(tfr.info["bads"]).union(*(t_.info["bads"] for t_ in all_tfr[1:])))