diff --git a/src/citibike/citibike_utils.py b/src/citibike/citibike_utils.py
index 99b5530..ee2e631 100644
--- a/src/citibike/citibike_utils.py
+++ b/src/citibike/citibike_utils.py
@@ -1,8 +1,8 @@
-from pyspark.sql.functions import unix_timestamp, col, round
+from pyspark.sql.functions import unix_timestamp, round
 
 def get_trip_duration_mins(spark, df, start_col, end_col, output_col):
 
     return df.withColumn(
         output_col,
-        round((unix_timestamp(col(end_col)) - unix_timestamp(col(start_col))) / 60, 2)
+        round((unix_timestamp(end_col) - unix_timestamp(start_col)) / 60, 2)
     )
\ No newline at end of file