diff --git a/schwab/client/base.py b/schwab/client/base.py
index b567f0d..e340b4b 100644
--- a/schwab/client/base.py
+++ b/schwab/client/base.py
@@ -1102,7 +1102,7 @@ def get_instruments(self, symbols, projection):
         projection = self.convert_enum(projection, self.Instrument.Projection)
 
         params = {
-                'symbol': ','.join(symbols),
+                'symbol': ','.join(symbols) if isinstance(symbols, list) else symbols,
                 'projection': projection,
         }