diff --git a/hvplot/converter.py b/hvplot/converter.py
index 9aadbc358..7802475e6 100644
--- a/hvplot/converter.py
+++ b/hvplot/converter.py
@@ -1485,7 +1485,7 @@ def _process_style(self, kwds, plot_opts):
         if 'color' in style_opts:
             color = style_opts['color']
         elif not isinstance(cmap, dict):
-            if cmap and any(c in cmap for c in categories):
+            if isinstance(cmap, str) and any(c in cmap for c in categories):
                 color = process_cmap(cmap or self._default_cmaps['categorical'], categorical=True)
             else:
                 color = cmap