diff --git a/crates/polars-plan/src/plans/conversion/join.rs b/crates/polars-plan/src/plans/conversion/join.rs
index 9e33f2079d11..0cd7c1563719 100644
--- a/crates/polars-plan/src/plans/conversion/join.rs
+++ b/crates/polars-plan/src/plans/conversion/join.rs
@@ -304,9 +304,9 @@ fn resolve_join_where(
         let original_right = right;
 
         for name in aexpr_to_leaf_names(right, ctxt.expr_arena) {
+            polars_ensure!(schema_right.contains(name.as_str()), ColumnNotFound: "could not find column {name} in the right table during join operation");
             if schema_left.contains(name.as_str()) {
                 let new_name = _join_suffix_name(name.as_str(), suffix.as_str());
-                polars_ensure!(schema_right.contains(name.as_str()), ColumnNotFound: "could not find column {name} in the right table during join operation");
 
                 right = rename_matching_aexpr_leaf_names(
                     right,
diff --git a/py-polars/tests/unit/operations/test_inequality_join.py b/py-polars/tests/unit/operations/test_inequality_join.py
index 428afa4f5c01..e639de2ac62e 100644
--- a/py-polars/tests/unit/operations/test_inequality_join.py
+++ b/py-polars/tests/unit/operations/test_inequality_join.py
@@ -5,6 +5,7 @@
 
 import hypothesis.strategies as st
 import numpy as np
+import pytest
 from hypothesis import given
 
 import polars as pl
@@ -436,9 +437,13 @@ def test_ie_join_with_floats(
     expr0 = _inequality_expression("dur", op1, "time")
     expr1 = _inequality_expression("rev", op2, "cost")
 
-    print(east, west)
     actual = east.join_where(west, expr0, expr1)
-    print(actual)
 
     expected = east.join(west, how="cross").filter(expr0 & expr1)
     assert_frame_equal(actual, expected, check_row_order=False, check_exact=True)
+
+
+def test_raise_on_suffixed_predicate_18604() -> None:
+    df = pl.DataFrame({"id": [1, 2]})
+    with pytest.raises(pl.exceptions.ColumnNotFoundError):
+        df.join_where(df, pl.col("id") >= pl.col("id_right"))