diff --git a/ravendb/documents/operations/counters.py b/ravendb/documents/operations/counters.py
index 14fab8ee..ba7b3f01 100644
--- a/ravendb/documents/operations/counters.py
+++ b/ravendb/documents/operations/counters.py
@@ -35,7 +35,7 @@ def __init__(
         if not counter_operation_type:
             raise ValueError(f"Missing counter_operation_type property in counter {counter_name}")
         if delta is None and counter_operation_type == CounterOperationType.INCREMENT:
-            raise ValueError(f"Missing delta property in counter {counter_name} of type {counter_operation_type}")
+            delta = 1
         self.counter_name = counter_name
         self.delta = delta
         self.counter_operation_type = counter_operation_type
diff --git a/ravendb/tests/counters_tests/test_counter_increment_default_delta.py b/ravendb/tests/counters_tests/test_counter_increment_default_delta.py
new file mode 100644
index 00000000..d7a2c2af
--- /dev/null
+++ b/ravendb/tests/counters_tests/test_counter_increment_default_delta.py
@@ -0,0 +1,58 @@
+"""
+Counter increment: omitting delta when incrementing defaults to delta=1.
+
+C# reference: SlowTests.Issues/Issues/RavenDB_22150.cs
+  IncrementByDefaultValue
+"""
+
+from ravendb.documents.operations.counters import (
+    CounterBatch,
+    CounterBatchOperation,
+    CounterOperation,
+    CounterOperationType,
+    DocumentCountersOperation,
+)
+from ravendb.infrastructure.entities import User
+from ravendb.tests.test_base import TestBase
+
+
+class TestRavenDB22150(TestBase):
+    def setUp(self):
+        super().setUp()
+
+    def test_increment_without_delta_defaults_to_one(self):
+        """
+        CounterOperation(INCREMENT) with no delta argument defaults to delta=1
+        on the client, matching the C# client's permissive default.
+
+        C# spec: IncrementByDefaultValue — sends a batch with two operations:
+          one with an explicit delta and one with no delta. The no-delta
+          operation should increment by 1.
+        """
+        with self.store.open_session() as session:
+            session.store(User(name="Danielle"), "users/1")
+            session.save_changes()
+
+        with self.store.open_session() as session:
+            session.counters_for("users/1").increment("likes", 10)
+            session.counters_for("users/1").increment("dislikes", 20)
+            session.save_changes()
+
+        # Single batch: explicit delta=5 for likes, no delta for dislikes (defaults to 1).
+        result = self.store.operations.send(
+            CounterBatchOperation(
+                CounterBatch(
+                    documents=[
+                        DocumentCountersOperation(
+                            document_id="users/1",
+                            operations=[
+                                CounterOperation("likes", CounterOperationType.INCREMENT, delta=5),
+                                CounterOperation("dislikes", CounterOperationType.INCREMENT),
+                            ],
+                        )
+                    ]
+                )
+            )
+        )
+
+        self.assertEqual(21, result.counters[1].total_value)