diff --git a/polars/polars-core/src/frame/asof_join/mod.rs b/polars/polars-core/src/frame/asof_join/mod.rs
index 7271678d8186..f6f84c13b1e8 100644
--- a/polars/polars-core/src/frame/asof_join/mod.rs
+++ b/polars/polars-core/src/frame/asof_join/mod.rs
@@ -30,6 +30,11 @@ pub struct AsOfOptions {
 fn check_asof_columns(a: &Series, b: &Series, check_sorted: bool) -> PolarsResult<()> {
     let dtype_a = a.dtype();
     let dtype_b = b.dtype();
+    polars_ensure!(
+        dtype_a.to_physical().is_numeric() && dtype_b.to_physical().is_numeric(),
+        InvalidOperation:
+        "asof join only supported on numeric/temporal keys"
+    );
     polars_ensure!(
         dtype_a == dtype_b,
         ComputeError: "mismatching key dtypes in asof-join: `{}` and `{}`",
diff --git a/py-polars/tests/unit/operations/test_join_asof.py b/py-polars/tests/unit/operations/test_join_asof.py
index bf99943a520a..9a86ca28cf21 100644
--- a/py-polars/tests/unit/operations/test_join_asof.py
+++ b/py-polars/tests/unit/operations/test_join_asof.py
@@ -2,6 +2,7 @@
 from typing import Any
 
 import numpy as np
+import pytest
 
 import polars as pl
 from polars.testing import assert_frame_equal
@@ -486,3 +487,12 @@ def test_asof_join_nearest_by_date() -> None:
 
     out = df1.join_asof(df2, on="asof_key", by="group", strategy="nearest")
     assert_frame_equal(out, expected)
+
+
+def test_asof_join_string_err() -> None:
+    left = pl.DataFrame({"date_str": ["2023/02/15"]}).sort("date_str")
+    right = pl.DataFrame(
+        {"date_str": ["2023/01/31", "2023/02/28"], "value": [0, 1]}
+    ).sort("date_str")
+    with pytest.raises(pl.InvalidOperationError):
+        left.join_asof(right, on="date_str")