diff --git a/Zip.xcodeproj/project.pbxproj b/Zip.xcodeproj/project.pbxproj
index 05b360c360e8c6843709520e7c69d2522c195843..9bd4a3a7b689fbe4c12d9abcb0e9d9978a865505 100644
--- a/Zip.xcodeproj/project.pbxproj
+++ b/Zip.xcodeproj/project.pbxproj
@@ -79,8 +79,6 @@
 		347E3AD81C1E04C900A11FD3 /* Zip.swift in Sources */ = {isa = PBXBuildFile; fileRef = 347E3AD71C1E04C900A11FD3 /* Zip.swift */; };
 		34940A241C58876200D41574 /* 3crBXeO.gif in Resources */ = {isa = PBXBuildFile; fileRef = 34940A221C58876200D41574 /* 3crBXeO.gif */; };
 		34940A251C58876200D41574 /* kYkLkPf.gif in Resources */ = {isa = PBXBuildFile; fileRef = 34940A231C58876200D41574 /* kYkLkPf.gif */; };
-		BBF824D51CA60383008FF3C5 /* bb8.cbz in Resources */ = {isa = PBXBuildFile; fileRef = BBF824D31CA60383008FF3C5 /* bb8.cbz */; };
-		BBF824D61CA60383008FF3C5 /* bb8.xyz in Resources */ = {isa = PBXBuildFile; fileRef = BBF824D41CA60383008FF3C5 /* bb8.xyz */; };
 /* End PBXBuildFile section */
 
 /* Begin PBXContainerItemProxy section */
@@ -145,8 +143,6 @@
 		347E3AD71C1E04C900A11FD3 /* Zip.swift */ = {isa = PBXFileReference; fileEncoding = 4; lastKnownFileType = sourcecode.swift; path = Zip.swift; sourceTree = "<group>"; };
 		34940A221C58876200D41574 /* 3crBXeO.gif */ = {isa = PBXFileReference; lastKnownFileType = image.gif; name = 3crBXeO.gif; path = Images/3crBXeO.gif; sourceTree = "<group>"; };
 		34940A231C58876200D41574 /* kYkLkPf.gif */ = {isa = PBXFileReference; lastKnownFileType = image.gif; name = kYkLkPf.gif; path = Images/kYkLkPf.gif; sourceTree = "<group>"; };
-		BBF824D31CA60383008FF3C5 /* bb8.cbz */ = {isa = PBXFileReference; lastKnownFileType = file; path = bb8.cbz; sourceTree = "<group>"; };
-		BBF824D41CA60383008FF3C5 /* bb8.xyz */ = {isa = PBXFileReference; lastKnownFileType = file; path = bb8.xyz; sourceTree = "<group>"; };
 /* End PBXFileReference section */
 
 /* Begin PBXFrameworksBuildPhase section */
@@ -266,8 +262,6 @@
 		347E3A821C1DFFB500A11FD3 /* ZipTests */ = {
 			isa = PBXGroup;
 			children = (
-				BBF824D31CA60383008FF3C5 /* bb8.cbz */,
-				BBF824D41CA60383008FF3C5 /* bb8.xyz */,
 				34940A221C58876200D41574 /* 3crBXeO.gif */,
 				34940A231C58876200D41574 /* kYkLkPf.gif */,
 				3443A3FC1C4AD199004AD173 /* bb8.zip */,
@@ -473,11 +467,9 @@
 			isa = PBXResourcesBuildPhase;
 			buildActionMask = 2147483647;
 			files = (
-				BBF824D51CA60383008FF3C5 /* bb8.cbz in Resources */,
 				34940A251C58876200D41574 /* kYkLkPf.gif in Resources */,
 				3443A3FD1C4AD199004AD173 /* bb8.zip in Resources */,
 				34940A241C58876200D41574 /* 3crBXeO.gif in Resources */,
-				BBF824D61CA60383008FF3C5 /* bb8.xyz in Resources */,
 			);
 			runOnlyForDeploymentPostprocessing = 0;
 		};
diff --git a/Zip/Zip.swift b/Zip/Zip.swift
index 083e0a3f8c283c341e2f5b5b0e0067717598b6ad..4eb9e4bdde9ceab5db4a52ec11f41b67aaeea208 100644
--- a/Zip/Zip.swift
+++ b/Zip/Zip.swift
@@ -292,6 +292,6 @@ public class Zip {
         
         guard let fileExtension = fileExtension else { return true }
         
-        return ["zip", "cbz"].contains(fileExtension)
+        return !["zip", "cbz"].contains(fileExtension)
     }
 }
\ No newline at end of file
diff --git a/ZipTests/ZipTests.swift b/ZipTests/ZipTests.swift
index d839220427bc9d05afb070204954452ec8675203..b420919d894c127962e7eaee33393edb033613c7 100644
--- a/ZipTests/ZipTests.swift
+++ b/ZipTests/ZipTests.swift
@@ -166,14 +166,14 @@ class ZipTests: XCTestCase {
     }
 
     func testFileExtensionIsInvalidForValidUrl() {
-        let fileUrl = NSBundle(forClass: ZipTests.self).URLForResource("bb8", withExtension: "cbz")
+        let fileUrl = NSURL(string: "file.cbz")
         let result = Zip.fileExtensionIsInvalid(fileUrl?.pathExtension)
-        XCTAssertTrue(result)
+        XCTAssertFalse(result)
     }
     
     func testFileExtensionIsInvalidForInvalidUrl() {
-        let fileUrl = NSBundle(forClass: ZipTests.self).URLForResource("bb8", withExtension: "xyz")
+        let fileUrl = NSURL(string: "file.xyz")
         let result = Zip.fileExtensionIsInvalid(fileUrl?.pathExtension)
-        XCTAssertFalse(result)
+        XCTAssertTrue(result)
     }
 }
diff --git a/ZipTests/bb8.cbz b/ZipTests/bb8.cbz
deleted file mode 100644
index 514266d193061fd851c447a37de608daef3136fa..0000000000000000000000000000000000000000
Binary files a/ZipTests/bb8.cbz and /dev/null differ
diff --git a/ZipTests/bb8.xyz b/ZipTests/bb8.xyz
deleted file mode 100644
index 514266d193061fd851c447a37de608daef3136fa..0000000000000000000000000000000000000000
Binary files a/ZipTests/bb8.xyz and /dev/null differ