diff --git a/brainstat/stats/SLM.py b/brainstat/stats/SLM.py
index c6dfa520..8ac161c2 100644
--- a/brainstat/stats/SLM.py
+++ b/brainstat/stats/SLM.py
@@ -322,7 +322,11 @@ def _surfstat_to_brainstat_rft(self) -> None:
                         )
                         yeo_names, _ = fetch_yeo_networks_metadata(7)
                         yeo_names.insert(0, "Undefined")
-                        yeo7_index = yeo7[self.P["peak"]["vertid"][i]]
+                        # vertid is stored as 1-based (inherited from SurfStat /
+                        # MATLAB conventions in peak_clus); subtract 1 before
+                        # indexing the 0-based yeo7 array (see #347).
+                        vertid = self.P["peak"]["vertid"][i]
+                        yeo7_index = yeo7[vertid - 1] if vertid is not None else None
                         if "yeo7" not in self.P["peak"]:
                             self.P["peak"]["yeo7"] = []
                         self.P["peak"]["yeo7"].append(np.take(yeo_names, yeo7_index))
diff --git a/brainstat_matlab/stats/@SLM/peak_clus.m b/brainstat_matlab/stats/@SLM/peak_clus.m
index 1581be96..5997c762 100755
--- a/brainstat_matlab/stats/@SLM/peak_clus.m
+++ b/brainstat_matlab/stats/@SLM/peak_clus.m
@@ -157,8 +157,10 @@
 
 function v_col = column_vector(v)
 % Converts the input vector to a column vector.
-arguments
-    v {mustBeVector}
+% Note: mustBeVector was introduced in MATLAB R2020b; an explicit check
+% is used here to keep compatibility with R2019b and R2020a (see #285).
+if ~isempty(v) && ~isvector(v)
+    error('column_vector:NotAVector', 'Input must be a vector.');
 end
 v_col = v(:);
 end