diff --git a/Editor/ReactiveObjects/ParameterAssignerPass.cs b/Editor/ReactiveObjects/ParameterAssignerPass.cs
index 5bfa59f7..1f3ff8c4 100644
--- a/Editor/ReactiveObjects/ParameterAssignerPass.cs
+++ b/Editor/ReactiveObjects/ParameterAssignerPass.cs
@@ -96,10 +96,10 @@ namespace nadena.dev.modular_avatar.core.editor
                 {
                     defaultValue = list.FirstOrDefault(m => m.isDefault && !m.automaticValue)?.Control?.value ?? 0;
 
-                    if (list.Count == 1)
-                        // If we have only a single entry, it's probably an on-off toggle, so we'll implicitly let 0
-                        // be the 'unselected' default value (if this is not default)
-                        defaultValue = 0;
+                    if (list.Count == 1 && list[0].isDefault && list[0].automaticValue)
+                        // If we have only a single entry, it's probably an on-off toggle, so we'll implicitly let 1
+                        // be the 'selected' default value (if this is default and automatic value)
+                        defaultValue = 1;
                 }
 
                 HashSet<int> usedValues = new();
@@ -124,11 +124,7 @@ namespace nadena.dev.modular_avatar.core.editor
                 {
                     if (mami.automaticValue)
                     {
-                        if (list.Count == 1)
-                        {
-                            mami.Control.value = 1;
-                        }
-                        else if (mami.isDefault)
+                        if (mami.isDefault)
                         {
                             mami.Control.value = defaultValue;
                         }
diff --git a/UnitTests~/ReactiveComponent/ParameterAssignment/AutoValueAssignmentTests.cs b/UnitTests~/ReactiveComponent/ParameterAssignment/AutoValueAssignmentTests.cs
index 62c3745c..ce0bd961 100644
--- a/UnitTests~/ReactiveComponent/ParameterAssignment/AutoValueAssignmentTests.cs
+++ b/UnitTests~/ReactiveComponent/ParameterAssignment/AutoValueAssignmentTests.cs
@@ -16,10 +16,14 @@ namespace UnitTests.ReactiveComponent.ParameterAssignment
         [Test]
         public void ManuallyAssignedParametersAreNotReplaced()
         {
-            TestAssignments(
-                new[] { (false, 1.0f), (false, 4.0f) },
-                new[] { 1.0f, 4.0f }
-            );
+            TestAssignments(new[] { (false, 1.0f) }, new[] { 1.0f });
+            TestAssignments(new[] { (false, 1.0f) }, new[] { 1.0f }, 0);
+
+            TestAssignments(new[] { (false, 4.0f) }, new[] { 4.0f });
+            TestAssignments(new[] { (false, 4.0f) }, new[] { 4.0f }, 0);
+
+            TestAssignments(new[] { (false, 1.0f), (false, 4.0f) }, new[] { 1.0f, 4.0f });
+            TestAssignments(new[] { (false, 1.0f), (false, 4.0f) }, new[] { 1.0f, 4.0f }, 0);
         }
 
         [Test]
@@ -98,6 +102,9 @@ namespace UnitTests.ReactiveComponent.ParameterAssignment
             {
                 Assert.AreEqual(expected, mami.Control.value);
             }
+
+            var expectedDefaultValue = defaultIndex.HasValue ? expectedAssignments[defaultIndex.Value] : 0;
+            Assert.AreEqual(expectedDefaultValue, avDesc.expressionParameters.parameters.Single().defaultValue);
         }
     }
 }
\ No newline at end of file