diff --git a/src/sql/src/plan/lowering/variadic_left.rs b/src/sql/src/plan/lowering/variadic_left.rs
index 72e3df39c3507..a36d14967605f 100644
--- a/src/sql/src/plan/lowering/variadic_left.rs
+++ b/src/sql/src/plan/lowering/variadic_left.rs
@@ -196,8 +196,9 @@ pub(crate) fn attempt_left_join_magic(
                 inc_metrics("voj_5");
                 return Ok(None);
             }
-            // Only columns not from the outer scope introduce bindings.
-            if left >= oa {
+            // Only columns not from the outer scope introduce bindings (`oa <= left`)
+            // And `left` needs to be a column in the left relation (`left < oa + ba`)
+            if oa <= left && left < oa + ba {
                 if let Some(bound) = bound_input {
                     // If left references come from different inputs, bail out.
                     if bound_to[left] != bound {
diff --git a/test/sqllogictest/variadic_outer_join.slt b/test/sqllogictest/variadic_outer_join.slt
new file mode 100644
index 0000000000000..ad89cedc5f36b
--- /dev/null
+++ b/test/sqllogictest/variadic_outer_join.slt
@@ -0,0 +1,200 @@
+# Copyright Materialize, Inc. and contributors. All rights reserved.
+#
+# Use of this software is governed by the Business Source License
+# included in the LICENSE file at the root of this repository.
+#
+# As of the Change Date specified in that file, in accordance with
+# the Business Source License, use of this software will be governed
+# by the Apache License, Version 2.0.
+
+mode cockroach
+
+statement ok
+CREATE TABLE a (k int)
+
+statement ok
+CREATE TABLE b (x int, y int, k int)
+
+statement ok
+CREATE TABLE c (k int)
+
+statement ok
+INSERT INTO a VALUES (1)
+
+# Only (5, 5, 100) satisfies the b.x = b.y filter.
+statement ok
+INSERT INTO b VALUES (5, 5, 100), (3, 7, 200)
+
+statement ok
+INSERT INTO c VALUES (100)
+
+# Baseline: with the variadic LEFT JOIN lowering disabled, the generic
+# outer-join lowering classifies `b.x = b.y` as a right-local filter and
+# produces the correct single-row result.
+simple conn=mz_system,user=mz_system
+ALTER SYSTEM SET enable_variadic_left_join_lowering TO false
+----
+COMPLETE 0
+
+query T multiline
+EXPLAIN OPTIMIZED PLAN FOR
+SELECT a.k, b.x, b.y, b.k, c.k
+FROM (a LEFT JOIN b ON b.x = b.y) LEFT JOIN c ON b.k = c.k
+----
+Explained Query:
+  With
+    cte l0 =
+      CrossJoin type=differential
+        ArrangeBy keys=[[]]
+          ReadStorage materialize.public.a
+        ArrangeBy keys=[[]]
+          Filter (#0 = #1)
+            ReadStorage materialize.public.b
+    cte l1 =
+      Union
+        Get l0
+        Project (#0, #2..=#4)
+          Map (null, null, null)
+            Join on=(#0 = #1) type=differential
+              ArrangeBy keys=[[#0]]
+                Union
+                  Negate
+                    Distinct project=[#0]
+                      Project (#0)
+                        Get l0
+                  Distinct project=[#0]
+                    ReadStorage materialize.public.a
+              ArrangeBy keys=[[#0]]
+                ReadStorage materialize.public.a
+    cte l2 =
+      ArrangeBy keys=[[#3{k}]]
+        Filter (#3{k}) IS NOT NULL
+          Get l1
+    cte l3 =
+      Project (#0..=#3)
+        Join on=(#3{k} = #4{k}) type=differential
+          Get l2
+          ArrangeBy keys=[[#0{k}]]
+            Filter (#0{k}) IS NOT NULL
+              ReadStorage materialize.public.c
+  Return
+    Union
+      Map (null)
+        Union
+          Negate
+            Project (#0..=#3)
+              Join on=(#3{k} = #4) type=differential
+                Get l2
+                ArrangeBy keys=[[#0]]
+                  Distinct project=[#0]
+                    Project (#3)
+                      Get l3
+          Get l1
+      Project (#0..=#3, #3)
+        Get l3
+
+Source materialize.public.a
+Source materialize.public.b
+  filter=((#0 = #1))
+Source materialize.public.c
+  filter=((#0{k}) IS NOT NULL)
+
+Target cluster: quickstart
+
+EOF
+
+query IIIII rowsort
+SELECT a.k, b.x, b.y, b.k, c.k
+FROM (a LEFT JOIN b ON b.x = b.y) LEFT JOIN c ON b.k = c.k
+----
+1  5  5  100  100
+
+# Re-enable the variadic lowering (the system default) and re-run the
+# same query. The expected result is unchanged.
+# But we have observed a buggy extra NULL-enriched row (in comments below)
+
+simple conn=mz_system,user=mz_system
+ALTER SYSTEM SET enable_variadic_left_join_lowering TO true
+----
+COMPLETE 0
+
+query T multiline
+EXPLAIN OPTIMIZED PLAN FOR
+SELECT a.k, b.x, b.y, b.k, c.k
+FROM (a LEFT JOIN b ON b.x = b.y) LEFT JOIN c ON b.k = c.k
+----
+Explained Query:
+  With
+    cte l0 =
+      CrossJoin type=differential
+        ArrangeBy keys=[[]]
+          ReadStorage materialize.public.a
+        ArrangeBy keys=[[]]
+          Filter (#0 = #1)
+            ReadStorage materialize.public.b
+    cte l1 =
+      Union
+        Get l0
+        Project (#0, #2..=#4)
+          Map (null, null, null)
+            Join on=(#0 = #1) type=differential
+              ArrangeBy keys=[[#0]]
+                Union
+                  Negate
+                    Distinct project=[#0]
+                      Project (#0)
+                        Get l0
+                  Distinct project=[#0]
+                    ReadStorage materialize.public.a
+              ArrangeBy keys=[[#0]]
+                ReadStorage materialize.public.a
+    cte l2 =
+      ArrangeBy keys=[[#3{k}]]
+        Filter (#3{k}) IS NOT NULL
+          Get l1
+    cte l3 =
+      Project (#0..=#3)
+        Join on=(#3{k} = #4{k}) type=differential
+          Get l2
+          ArrangeBy keys=[[#0{k}]]
+            Filter (#0{k}) IS NOT NULL
+              ReadStorage materialize.public.c
+  Return
+    Union
+      Map (null)
+        Union
+          Negate
+            Project (#0..=#3)
+              Join on=(#3{k} = #4) type=differential
+                Get l2
+                ArrangeBy keys=[[#0]]
+                  Distinct project=[#0]
+                    Project (#3)
+                      Get l3
+          Get l1
+      Project (#0..=#3, #3)
+        Get l3
+
+Source materialize.public.a
+Source materialize.public.b
+  filter=((#0 = #1))
+Source materialize.public.c
+  filter=((#0{k}) IS NOT NULL)
+
+Target cluster: quickstart
+
+EOF
+
+query IIIII rowsort
+SELECT a.k, b.x, b.y, b.k, c.k
+FROM (a LEFT JOIN b ON b.x = b.y) LEFT JOIN c ON b.k = c.k
+----
+1  5  5  100  100
+
+# 1  NULL  NULL  NULL  NULL
+
+query IIII rowsort
+SELECT a.k, b.k, b.x, c.k
+FROM (a LEFT JOIN b ON a.k = b.k AND b.x = b.y) LEFT JOIN c ON a.k = c.k
+----
+1  NULL  NULL  NULL