diff --git a/.changeset/stable-filter-selector.md b/.changeset/stable-filter-selector.md
new file mode 100644
index 000000000..274c288f3
--- /dev/null
+++ b/.changeset/stable-filter-selector.md
@@ -0,0 +1,5 @@
+---
+"@equinor/fusion-react-filter": patch
+---
+
+Prevent `FilterOptionHeader` from entering an infinite render loop after upgrading `@equinor/fusion-observable` by keeping its selection count selector stable across renders.
diff --git a/packages/filter/src/components/filter/FilterOptionHeader.tsx b/packages/filter/src/components/filter/FilterOptionHeader.tsx
index 2f7cdafcf..3e9178209 100644
--- a/packages/filter/src/components/filter/FilterOptionHeader.tsx
+++ b/packages/filter/src/components/filter/FilterOptionHeader.tsx
@@ -14,6 +14,8 @@ type FilterHeaderProps = {
   readonly title: string;
 };
 
+const getSelectedCount = (selection?: Set<unknown>): number => selection?.size ?? 0;
+
 const Styled = {
   Root: styled.div`
     display: flex;
@@ -63,7 +65,7 @@ export const FilterOptionHeader = (props: FilterHeaderProps): ReactElement => {
   const { options$, selection$ } = useFilterOptionContext();
   const optionCount = Object.keys(useObservableState(options$).value || {}).length;
   const { value: selectedCount } = useObservableState(
-    useObservableSelector(selection$, (x) => (x ?? new Set()).size),
+    useObservableSelector(selection$, getSelectedCount),
     { initial: 0 },
   );