diff --git a/bqplot/traits.py b/bqplot/traits.py
index 95f4efb3f..dafaddfbb 100644
--- a/bqplot/traits.py
+++ b/bqplot/traits.py
@@ -239,7 +239,9 @@ def dataframe_to_json(df, obj):
     if df is None:
         return None
     else:
-        return df.to_dict(orient='records')
+        # Replacing NaNs with None as it's not valid JSON
+        cleandf = df.fillna(np.nan).replace([np.nan], [None])
+        return cleandf.to_dict(orient='records')
 
 
 dataframe_serialization = dict(to_json=dataframe_to_json, from_json=dataframe_from_json)
diff --git a/js/src/Map.ts b/js/src/Map.ts
index d0b109461..4ff9164f0 100644
--- a/js/src/Map.ts
+++ b/js/src/Map.ts
@@ -454,7 +454,6 @@ export class Map extends Mark {
     } else if (
       color_data[d.id] === undefined ||
       color_data[d.id] === null ||
-      color_data[d.id] === 'nan' ||
       color_scale === undefined
     ) {
       return colors.default_color;
diff --git a/js/src/MarketMap.ts b/js/src/MarketMap.ts
index 724c3380d..96d526c9b 100644
--- a/js/src/MarketMap.ts
+++ b/js/src/MarketMap.ts
@@ -791,9 +791,15 @@ export class MarketMap extends Figure {
           .append('td')
           .attr('class', 'tooltiptext')
           .text((datum, index) => {
-            return ref_data === null || ref_data === undefined
-              ? null
-              : that.tooltip_formats[index](ref_data[datum]);
+            if (ref_data === null || ref_data === undefined) {
+              return null;
+            }
+
+            if (ref_data[datum] === null || ref_data[datum] === undefined) {
+              return 'N/A';
+            }
+
+            return that.tooltip_formats[index](ref_data[datum]);
           });
       }
       this.popper.enableEventListeners();
diff --git a/test-environment.yml b/test-environment.yml
index be28aa524..c953b056f 100644
--- a/test-environment.yml
+++ b/test-environment.yml
@@ -11,7 +11,6 @@ dependencies:
     - numpy >=1.10.4,<2.0.0
     - pandas >=1.0.0,<2.0.0
     - scipy
-    - jupyter
     - jupyterlab=3.0.11  # to build the lab federated bundle
     - jupyter-packaging # to build the wheel
     - pytest