diff --git a/+io/mapData2H5.m b/+io/mapData2H5.m
index 3287e9a7..41a1b363 100644
--- a/+io/mapData2H5.m
+++ b/+io/mapData2H5.m
@@ -6,6 +6,11 @@
 forceArray = any(strcmp('forceArray', varargin));
 forceChunked = any(strcmp('forceChunking', varargin));
 
+if iscell(data)
+    assert(iscellstr(data), 'NWB:MapData:NonCellStr', ['Cell arrays must be ' ...
+        'cell arrays of character vectors. Cell arrays of other types are ' ...
+        'not supported.']);
+end
 tid = io.getBaseType(class(data));
 
 % max size is always unlimited