diff --git a/Sources/OpenSwiftUI/Core/View/ViewGraph.swift b/Sources/OpenSwiftUI/Core/View/ViewGraph.swift
index 067d235e..e4f204a7 100644
--- a/Sources/OpenSwiftUI/Core/View/ViewGraph.swift
+++ b/Sources/OpenSwiftUI/Core/View/ViewGraph.swift
@@ -47,7 +47,9 @@ final class ViewGraph: GraphHost {
         // FIXME: TO BE CONFIRMED
         set { setPreferenceBridge(to: newValue, isInvalidating: newValue == nil) }
     }
+    #if canImport(Darwin) // FIXME: See #39
     var bridgedPreferences: [(AnyPreferenceKey.Type, OGAttribute)] = []
+    #endif
     // TODO
     
     init<Body: View>(rootViewType: Body.Type, requestedOutputs: Outputs) {
diff --git a/Sources/OpenSwiftUI/Data/Preference/PreferenceBridge.swift b/Sources/OpenSwiftUI/Data/Preference/PreferenceBridge.swift
index 7ac2dffd..2ce12422 100644
--- a/Sources/OpenSwiftUI/Data/Preference/PreferenceBridge.swift
+++ b/Sources/OpenSwiftUI/Data/Preference/PreferenceBridge.swift
@@ -25,7 +25,8 @@ final class PreferenceBridge {
     init() {
         viewGraph = GraphHost.currentHost as! ViewGraph
     }
-
+    
+    #if canImport(Darwin) // FIXME: See #39
     func addValue(_ value: OGAttribute, for keyType: AnyPreferenceKey.Type) {
         struct AddValue: PreferenceKeyVisitor {
             var combiner: OGAttribute
@@ -191,6 +192,7 @@ final class PreferenceBridge {
             }
         }
     }
+    #endif
 }
 
 private struct MergePreferenceKeys: Rule, AsyncAttribute {
diff --git a/Sources/OpenSwiftUI/Data/Preference/PreferencesCombiner.swift b/Sources/OpenSwiftUI/Data/Preference/PreferencesCombiner.swift
index 5e8a0d74..c3f99fe5 100644
--- a/Sources/OpenSwiftUI/Data/Preference/PreferencesCombiner.swift
+++ b/Sources/OpenSwiftUI/Data/Preference/PreferencesCombiner.swift
@@ -42,6 +42,7 @@ struct HostPreferencesCombiner: Rule, AsyncAttribute {
         @WeakAttribute var values: PreferenceList?
     }
 
+    #if canImport(Darwin) // FIXME: See #39
     mutating func addChild(keys: Attribute<PreferenceKeys>, values: Attribute<PreferenceList>) {
         let weakKeys = OGWeakAttribute(keys.identifier)
         let weakValues = OGWeakAttribute(values.identifier)
@@ -52,6 +53,7 @@ struct HostPreferencesCombiner: Rule, AsyncAttribute {
             children.append(child)
         }
     }
+    #endif
 
     private struct CombineValues: PreferenceKeyVisitor {
         var children: [Child]
diff --git a/Sources/OpenSwiftUI/Data/Preference/PreferencesOutputs.swift b/Sources/OpenSwiftUI/Data/Preference/PreferencesOutputs.swift
index 33a9c934..c2f98712 100644
--- a/Sources/OpenSwiftUI/Data/Preference/PreferencesOutputs.swift
+++ b/Sources/OpenSwiftUI/Data/Preference/PreferencesOutputs.swift
@@ -11,16 +11,17 @@ internal import OpenGraphShims
 struct PreferencesOutputs {
     private var preferences: [KeyValue] = []
     private var debugProperties: _ViewDebug.Properties = []
-    
-    func contains<Key: PreferenceKey>(_ key: Key.Type) -> Bool {
+
+    func contains<Key: PreferenceKey>(_: Key.Type) -> Bool {
         contains(_AnyPreferenceKey<Key>.self)
     }
-    
+
     func contains(_ key: AnyPreferenceKey.Type) -> Bool {
         preferences.contains { $0.key == key }
     }
-    
-    subscript<Key: PreferenceKey>(_ keyType: Key.Type) -> Attribute<Key.Value>? {
+
+    #if canImport(Darwin) // FIXME: See #39
+    subscript<Key: PreferenceKey>(_: Key.Type) -> Attribute<Key.Value>? {
         get {
             let value = self[anyKey: _AnyPreferenceKey<Key>.self]
             return value.map { Attribute(identifier: $0) }
@@ -29,7 +30,7 @@ struct PreferencesOutputs {
             self[anyKey: _AnyPreferenceKey<Key>.self] = newValue?.identifier
         }
     }
-    
+
     subscript(anyKey keyType: AnyPreferenceKey.Type) -> OGAttribute? {
         get { preferences.first { $0.key == keyType }?.value }
         set {
@@ -51,11 +52,19 @@ struct PreferencesOutputs {
             }
         }
     }
+    #else
+    subscript<Key: PreferenceKey>(_: Key.Type) -> Attribute<Key.Value>? {
+        get { fatalError("See #39") }
+        set { fatalError("See #39") }
+    }
+    #endif
 }
 
 extension PreferencesOutputs {
     private struct KeyValue {
         var key: AnyPreferenceKey.Type
+        #if canImport(Darwin) // FIXME: See #39
         var value: OGAttribute
+        #endif
     }
 }