diff --git a/dynamicviz/viz.py b/dynamicviz/viz.py
index c341716..5980619 100644
--- a/dynamicviz/viz.py
+++ b/dynamicviz/viz.py
@@ -416,9 +416,10 @@ def stacked(
         if vmax is None:
             vmax = np.max(df[label])
 
-    # automatically set alpha based on heuristic
-    if alpha is None:
-        alpha = 0.2 / (df.shape[0] / 1000)
+    # automatically set alpha based on heuristic and cap at 1.0 for small datasets
+    if alpha is None:
+        alpha = 0.2 / (df.shape[0] / 1000)
+        alpha = min(alpha, 1.0)
 
     fig = plt.figure(figsize=(width, height))