diff --git a/Sources/XcodeGenKit/CacheFile.swift b/Sources/XcodeGenKit/CacheFile.swift
index eb8d697e..b8afbb47 100644
--- a/Sources/XcodeGenKit/CacheFile.swift
+++ b/Sources/XcodeGenKit/CacheFile.swift
@@ -9,7 +9,7 @@ public class CacheFile {
 
         guard #available(OSX 10.13, *) else { return nil }
 
-        let files = project.allFiles
+        let files = Set(project.allFiles)
             .map { ((try? $0.relativePath(from: project.basePath)) ?? $0).string }
             .sorted { $0.localizedStandardCompare($1) == .orderedAscending }
             .joined(separator: "\n")