diff --git a/heatmap-tool/backend/main.py b/heatmap-tool/backend/main.py
index dac02b78..47d0c17a 100644
--- a/heatmap-tool/backend/main.py
+++ b/heatmap-tool/backend/main.py
@@ -132,6 +132,9 @@ async def get_heatmap_data(request: FilterRequest):
         # Rename columns to match frontend expectations ('lon' and 'lat')
         merged_df.rename(columns={'x': 'lon', 'y': 'lat'}, inplace=True)
         
+        # Also rename the original PLZ column to the consistent name 'plz'
+        merged_df.rename(columns={plz_column_name: 'plz'}, inplace=True)
+        
         # Convert to the required JSON format
         heatmap_data = merged_df[['plz', 'lat', 'lon', 'count']].to_dict(orient='records')