diff --git a/Project.toml b/Project.toml
index 1a341c14..82ec2e17 100644
--- a/Project.toml
+++ b/Project.toml
@@ -24,7 +24,7 @@ AssetRegistry = "0.1.0"
 FunctionalCollections = "0.5.0"
 JSExpr = "0.5"
 JSON = "0.18, 0.19, 0.20, 0.21"
-Observables = "0.3, 0.4, 0.5"
+Observables = "0.4, 0.5"
 Requires = "0.4.4, 0.5, 1.0.0"
 WebSockets = "1.5.0"
 Widgets = "0.6.2"
diff --git a/src/scope.jl b/src/scope.jl
index f80a6bd5..92491e6d 100644
--- a/src/scope.jl
+++ b/src/scope.jl
@@ -332,31 +332,21 @@ struct SyncCallback
 end
 
 (s::SyncCallback)(xs...) = s.f(xs...)
+
 """
 Set observable without synchronizing with the counterpart on the browser.
 
 This is mostly used to update observables in response to updates sent from th
 browser (so that we aren't sending the same update *back* to the browser).
 """
-function set_nosync end
-
-if isdefined(Observables, :setexcludinghandlers)
-    # Observables <=0.3
-    function set_nosync(ob, val)
-        Observables.setexcludinghandlers(ob, val, x -> !(x isa SyncCallback))
-        return
-    end
-else
-    # Observables >=0.4
-    function set_nosync(ob, val)
-        Observables.setexcludinghandlers!(ob, val)
-        for f in listeners(ob)
-            if !(f isa SyncCallback)
-                Base.invokelatest(f, val)
-            end
+function set_nosync(ob, val)
+    Observables.setexcludinghandlers!(ob, val)
+    for (_, f) in listeners(ob)
+        if !(f isa SyncCallback)
+            Base.invokelatest(f, val)
         end
-        return
     end
+    return
 end
 
 const lifecycle_commands = ["scope_created"]