diff --git a/smithy-build/src/main/java/software/amazon/smithy/build/PluginContext.java b/smithy-build/src/main/java/software/amazon/smithy/build/PluginContext.java
index a416f7c7caa..f2408bd58a7 100644
--- a/smithy-build/src/main/java/software/amazon/smithy/build/PluginContext.java
+++ b/smithy-build/src/main/java/software/amazon/smithy/build/PluginContext.java
@@ -254,16 +254,17 @@ private int findOffsetFromStart(String location) {
 
     @Override
     public Builder toBuilder() {
-        return builder()
-                .projection(projectionName, projection)
+        Builder builder =  builder()
                 .model(model)
-                .originalModel(originalModel)
                 .events(events)
                 .settings(settings)
                 .fileManifest(fileManifest)
                 .pluginClassLoader(pluginClassLoader)
                 .sources(sources)
                 .artifactName(artifactName);
+        getProjection().ifPresent(config -> builder.projection(projectionName, config));
+        getOriginalModel().ifPresent(builder::originalModel);
+        return builder;
     }
 
     /**
diff --git a/smithy-build/src/test/java/software/amazon/smithy/build/PluginContextTest.java b/smithy-build/src/test/java/software/amazon/smithy/build/PluginContextTest.java
index aa26b499e4e..f70e7724be9 100644
--- a/smithy-build/src/test/java/software/amazon/smithy/build/PluginContextTest.java
+++ b/smithy-build/src/test/java/software/amazon/smithy/build/PluginContextTest.java
@@ -82,4 +82,16 @@ public void convertsToBuilder() {
         assertThat(context.getSources(), equalTo(context2.getSources()));
         assertThat(context.getEvents(), equalTo(context2.getEvents()));
     }
+
+    @Test
+    public void roundTripsDefaults() {
+        PluginContext before = PluginContext.builder()
+                .model(Model.builder().build())
+                .fileManifest(new MockManifest())
+                .build();
+        PluginContext after = before.toBuilder().build();
+        assertThat(before.getModel(), equalTo(after.getModel()));
+        assertThat(before.getFileManifest(), equalTo(after.getFileManifest()));
+        assertThat(before.getProjectionName(), equalTo(after.getProjectionName()));
+    }
 }