diff --git a/ckanext/charts/chart_builders/plotly.py b/ckanext/charts/chart_builders/plotly.py
index 8ad1ace..2ed89c2 100644
--- a/ckanext/charts/chart_builders/plotly.py
+++ b/ckanext/charts/chart_builders/plotly.py
@@ -246,10 +246,11 @@ def build_scatter_chart(self) -> Any:
         if self.settings.get("skip_null_values"):
             self.df = self.df.loc[self.df[self.settings["y"]] != 0]
 
-        if self.df[self.settings["size"]].dtype not in ["int64", "float64"]:
+        size_column = self.df[self.settings.get("size", self.df.columns[0])]
+        is_numeric = pd.api.types.is_numeric_dtype(size_column)
+        if not is_numeric:
             raise exception.ChartBuildError(
-                """The 'size' source should be a field of positive integer 
-                or float type."""
+                "The 'Size' source should be a field of numeric type.",
             )
 
         fig = px.scatter(
diff --git a/ckanext/charts/tests/test_builders.py b/ckanext/charts/tests/test_builders.py
index 640f1e7..d52f247 100644
--- a/ckanext/charts/tests/test_builders.py
+++ b/ckanext/charts/tests/test_builders.py
@@ -85,6 +85,8 @@ def test_build_scatter(self, data_frame):
                 "engine": "plotly",
                 "x": "name",
                 "y": "age",
+                "size": "age",
+                "size_max": 100,
             },
             data_frame,
         )