diff --git a/src/polymarket/models/data/activity.py b/src/polymarket/models/data/activity.py
index dc88a8b..b0f6a11 100644
--- a/src/polymarket/models/data/activity.py
+++ b/src/polymarket/models/data/activity.py
@@ -121,7 +121,7 @@ class TradeActivity(_KnownActivityBase):
     outcome_index: int = Field(validation_alias="outcomeIndex")
     title: str
     slug: str
-    icon: str
+    icon: str | None = None
     event_slug: str = Field(validation_alias="eventSlug")
 
     @field_validator("condition_id", mode="before")
@@ -140,7 +140,7 @@ class _MarketEventActivity(_KnownActivityBase):
     amount: Decimal
     title: str
     slug: str
-    icon: str
+    icon: str | None = None
     event_slug: str = Field(validation_alias="eventSlug")
 
     @field_validator("condition_id", mode="before")
@@ -284,7 +284,7 @@ def _normalize_activity_payload(data: dict[str, Any]) -> dict[str, Any]:
     if normalized.get("outcomeIndex") == 999:
         normalized.pop("outcomeIndex", None)
 
-    for sentinel_key in ("conditionId", "asset", "side", "outcome"):
+    for sentinel_key in ("conditionId", "asset", "side", "outcome", "icon"):
         if normalized.get(sentinel_key) == "":
             normalized.pop(sentinel_key, None)
 
diff --git a/tests/unit/test_data_activity.py b/tests/unit/test_data_activity.py
index dbd2331..b6df610 100644
--- a/tests/unit/test_data_activity.py
+++ b/tests/unit/test_data_activity.py
@@ -125,6 +125,18 @@ def test_empty_string_sentinels_drop_to_none_on_trade_raises() -> None:
         parse_activity(payload)
 
 
+def test_trade_empty_icon_normalizes_to_none() -> None:
+    activity = parse_activity(_trade_payload(icon=""))
+    assert isinstance(activity, TradeActivity)
+    assert activity.icon is None
+
+
+def test_market_event_empty_icon_normalizes_to_none() -> None:
+    activity = parse_activity(_market_event_payload("SPLIT", icon=""))
+    assert isinstance(activity, SplitActivity)
+    assert activity.icon is None
+
+
 def test_market_event_variants_parse() -> None:
     for activity_type, expected_class in [
         ("SPLIT", SplitActivity),