diff --git a/crates/polars-lazy/src/tests/io.rs b/crates/polars-lazy/src/tests/io.rs
index 8d0d7a0612ba..089b1b114742 100644
--- a/crates/polars-lazy/src/tests/io.rs
+++ b/crates/polars-lazy/src/tests/io.rs
@@ -242,6 +242,7 @@ fn test_csv_globbing() -> PolarsResult<()> {
     let df = lf.clone().collect()?;
     assert_eq!(df.shape(), (100, 4));
     let df = LazyCsvReader::new(glob).finish()?.slice(20, 60).collect()?;
+    dbg!(&full_df, &df);
     assert!(full_df.slice(20, 60).frame_equal(&df));
 
     let mut expr_arena = Arena::with_capacity(16);
diff --git a/crates/polars-plan/src/logical_plan/optimizer/slice_pushdown_lp.rs b/crates/polars-plan/src/logical_plan/optimizer/slice_pushdown_lp.rs
index 6a929c369af5..cd6f979c37f3 100644
--- a/crates/polars-plan/src/logical_plan/optimizer/slice_pushdown_lp.rs
+++ b/crates/polars-plan/src/logical_plan/optimizer/slice_pushdown_lp.rs
@@ -185,10 +185,12 @@ impl SlicePushDown {
             }
             (Union {mut inputs, mut options }, Some(state)) => {
                 options.slice = Some((state.offset, state.len as usize));
-                for input in &mut inputs {
-                    let input_lp = lp_arena.take(*input);
-                    let input_lp = self.pushdown(input_lp, Some(state), lp_arena, expr_arena)?;
-                    lp_arena.replace(*input, input_lp);
+                if state.offset == 0 {
+                    for input in &mut inputs {
+                        let input_lp = lp_arena.take(*input);
+                        let input_lp = self.pushdown(input_lp, Some(state), lp_arena, expr_arena)?;
+                        lp_arena.replace(*input, input_lp);
+                    }
                 }
                 Ok(Union {inputs, options})
             },