diff --git a/Silica ViewerTests/Silica_ViewerTests.swift b/Silica ViewerTests/Silica_ViewerTests.swift
index e59b2a0..243051d 100644
--- a/Silica ViewerTests/Silica_ViewerTests.swift	
+++ b/Silica ViewerTests/Silica_ViewerTests.swift	
@@ -26,6 +26,10 @@ class Silica_ViewerTests: XCTestCase {
         XCTAssert(document.parsePairString("{-1, -1}")! == (-1, -1))
         XCTAssert(document.parsePairString("{255, 255}")! == (255, 255))
         XCTAssert(document.parsePairString("{255}") == nil)
+        
+        XCTAssert(document.parseChunkFilename("1~1.chunk")! == (1, 2))
+        XCTAssert(document.parseChunkFilename("10~2.chunk")! == (10, 3))
+        XCTAssert(document.parseChunkFilename("~1.chunk") == nil)
     }
 
     func testPerformanceExample() throws {
diff --git a/SilicaViewer/Document.swift b/SilicaViewer/Document.swift
index 93ea89d..95a12b8 100644
--- a/SilicaViewer/Document.swift
+++ b/SilicaViewer/Document.swift
@@ -135,7 +135,7 @@ class Document: NSDocument {
     /*
      Parses the chunk filename, ex. 1~1 to integer coordinates.
      */
-    func parseChunkFilename(filename: String) -> (Int, Int)? {
+    func parseChunkFilename(_ filename: String) -> (Int, Int)? {
         let pathURL = URL(fileURLWithPath: filename)
         let pathComponents = pathURL.lastPathComponent.replacingOccurrences(of: ".chunk", with: "").components(separatedBy: "~")
         
@@ -301,7 +301,7 @@ class Document: NSDocument {
                     
                 let threadEntry = threadArchive[chunkPaths[i]]
 
-                guard let (x, y) = parseChunkFilename(filename: threadEntry!.path) else {
+                guard let (x, y) = parseChunkFilename(threadEntry!.path) else {
                     return
                 }