diff --git a/src/main/java/io/github/ascopes/protobufmavenplugin/generate/SourceCodeGenerator.java b/src/main/java/io/github/ascopes/protobufmavenplugin/generate/SourceCodeGenerator.java
index 12d36d63..c9d4ab13 100644
--- a/src/main/java/io/github/ascopes/protobufmavenplugin/generate/SourceCodeGenerator.java
+++ b/src/main/java/io/github/ascopes/protobufmavenplugin/generate/SourceCodeGenerator.java
@@ -95,7 +95,7 @@ public boolean generate(GenerationRequest request) throws ResolutionException, I
         .importPaths(importPaths
             .stream()
             .map(ProtoFileListing::getProtoFilesRoot)
-            .collect(Collectors.toUnmodifiableSet()))
+            .collect(Collectors.toSet()))
         .importPaths(request.getSourceRoots())
         .plugins(plugins, request.getOutputDirectory());