diff --git a/Signal.xcodeproj/project.pbxproj b/Signal.xcodeproj/project.pbxproj
index 67a4943a8..9b359b79f 100644
--- a/Signal.xcodeproj/project.pbxproj
+++ b/Signal.xcodeproj/project.pbxproj
@@ -431,6 +431,7 @@
 		4C13C9F620E57BA30089A98B /* ColorPickerViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C13C9F520E57BA30089A98B /* ColorPickerViewController.swift */; };
 		4C20B2B720CA0034001BAC90 /* ThreadViewModel.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4542DF51208B82E9007B4E76 /* ThreadViewModel.swift */; };
 		4C20B2B920CA10DE001BAC90 /* ConversationSearchViewController.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C20B2B820CA10DE001BAC90 /* ConversationSearchViewController.swift */; };
+		4C3EF802210918740007EBF7 /* SSKEnvelopeTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C3EF801210918740007EBF7 /* SSKEnvelopeTest.swift */; };
 		4C4AEC4520EC343B0020E72B /* DismissableTextField.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C4AEC4420EC343B0020E72B /* DismissableTextField.swift */; };
 		4C4BC6C32102D697004040C9 /* ContactDiscoveryOperationTest.swift in Sources */ = {isa = PBXBuildFile; fileRef = 4C4BC6C22102D697004040C9 /* ContactDiscoveryOperationTest.swift */; };
 		4C6F527C20FFE8400097DEEE /* SignalUBSan.supp in Resources */ = {isa = PBXBuildFile; fileRef = 4C6F527B20FFE8400097DEEE /* SignalUBSan.supp */; };
@@ -1110,6 +1111,7 @@
 		4C11AA4F20FD59C700351FBD /* MessageStatusView.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = MessageStatusView.swift; sourceTree = "<group>"; };
 		4C13C9F520E57BA30089A98B /* ColorPickerViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ColorPickerViewController.swift; sourceTree = "<group>"; };
 		4C20B2B820CA10DE001BAC90 /* ConversationSearchViewController.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = ConversationSearchViewController.swift; sourceTree = "<group>"; };
+		4C3EF801210918740007EBF7 /* SSKEnvelopeTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = SSKEnvelopeTest.swift; sourceTree = "<group>"; };
 		4C4AEC4420EC343B0020E72B /* DismissableTextField.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; path = DismissableTextField.swift; sourceTree = "<group>"; };
 		4C4BC6C22102D697004040C9 /* ContactDiscoveryOperationTest.swift */ = {isa = PBXFileReference; lastKnownFileType = sourcecode.swift; name = ContactDiscoveryOperationTest.swift; path = contact/ContactDiscoveryOperationTest.swift; sourceTree = "<group>"; };
 		4C6F527B20FFE8400097DEEE /* SignalUBSan.supp */ = {isa = PBXFileReference; lastKnownFileType = text; path = SignalUBSan.supp; sourceTree = "<group>"; };
@@ -2109,6 +2111,14 @@
 			path = Speakerbox;
 			sourceTree = "<group>";
 		};
+		4C3EF8002109184A0007EBF7 /* SSKTests */ = {
+			isa = PBXGroup;
+			children = (
+				4C3EF801210918740007EBF7 /* SSKEnvelopeTest.swift */,
+			);
+			path = SSKTests;
+			sourceTree = "<group>";
+		};
 		76EB03C118170B33006006FC /* src */ = {
 			isa = PBXGroup;
 			children = (
@@ -2284,6 +2294,7 @@
 		B660F66C1C29867F00687D6E /* test */ = {
 			isa = PBXGroup;
 			children = (
+				4C3EF8002109184A0007EBF7 /* SSKTests */,
 				34C6B0A41FA0E46F00D35993 /* Assets */,
 				B660F6731C29867F00687D6E /* call */,
 				B660F6751C29867F00687D6E /* contact */,
@@ -3454,6 +3465,7 @@
 				B660F6DA1C29868000687D6E /* ExceptionsTest.m in Sources */,
 				B660F6DB1C29868000687D6E /* FunctionalUtilTest.m in Sources */,
 				45E7A6A81E71CA7E00D44FB5 /* DisplayableTextFilterTest.swift in Sources */,
+				4C3EF802210918740007EBF7 /* SSKEnvelopeTest.swift in Sources */,
 				452D1AF12081059C00A67F7F /* StringAdditionsTest.swift in Sources */,
 				4C4BC6C32102D697004040C9 /* ContactDiscoveryOperationTest.swift in Sources */,
 				B660F6BB1C29868000687D6E /* OWSContactsManagerTest.m in Sources */,
diff --git a/Signal/test/SSKTests/SSKEnvelopeTest.swift b/Signal/test/SSKTests/SSKEnvelopeTest.swift
new file mode 100644
index 000000000..fa1aff2f9
--- /dev/null
+++ b/Signal/test/SSKTests/SSKEnvelopeTest.swift
@@ -0,0 +1,68 @@
+//
+//  Copyright (c) 2018 Open Whisper Systems. All rights reserved.
+//
+
+import XCTest
+
+import SignalServiceKit
+import SwiftProtobuf
+
+class SSKEnvelopeTest: XCTestCase {
+
+    override func setUp() {
+        super.setUp()
+        // Put setup code here. This method is called before the invocation of each test method in the class.
+    }
+
+    override func tearDown() {
+        // Put teardown code here. This method is called after the invocation of each test method in the class.
+        super.tearDown()
+    }
+
+    func testParse_EmptyData() {
+        let data = Data()
+        XCTAssertThrowsError(try SSKEnvelope(serializedData: data))
+    }
+
+    func testParse_UnparseableData() {
+        let data = "asdf".data(using: .utf8)!
+        XCTAssertThrowsError(try SSKEnvelope(serializedData: data)) { error in
+            XCTAssert(error is SwiftProtobuf.BinaryDecodingError)
+        }
+    }
+
+    func testParse_ValidData() {
+        // `encodedData` was derived thus:
+        //     let builder = OWSSignalServiceProtosEnvelopeBuilder()
+        //     builder.setTimestamp(NSDate.ows_millisecondTimeStamp())
+        //     builder.setSource("+15551231234")
+        //     builder.setSourceDevice(1)
+        //     builder.setType(OWSSignalServiceProtosEnvelopeType.ciphertext)
+        //     let encodedData = builder.build().data()!.base64EncodedString()
+        let encodedData = "CAESDCsxNTU1MTIzMTIzNCjKm4WazSw4AQ=="
+        let data = Data(base64Encoded: encodedData)!
+
+        XCTAssertNoThrow(try SSKEnvelope(serializedData: data))
+    }
+
+    func testParse_invalidData() {
+        // `encodedData` was derived thus:
+        //     let builder = OWSSignalServiceProtosEnvelopeBuilder()
+        //     builder.setTimestamp(NSDate.ows_millisecondTimeStamp())
+        //     builder.setSource("+15551231234")
+        //     builder.setSourceDevice(1)
+        //     // MISSING TYPE!
+        //     let encodedData = builder.build().data()!.base64EncodedString()
+        let encodedData = "EgwrMTU1NTEyMzEyMzQojdmOms0sOAE="
+        let data = Data(base64Encoded: encodedData)!
+
+        XCTAssertThrowsError(try SSKEnvelope(serializedData: data)) { (error) -> Void in
+            switch error {
+            case SSKEnvelope.EnvelopeError.invalidProtobuf:
+                break
+            default:
+                XCTFail("unexpected error: \(error)")
+            }
+        }
+    }
+}
diff --git a/SignalServiceKit/src/Protos/ProtoWrappers/SSKEnvelope.swift b/SignalServiceKit/src/Protos/ProtoWrappers/SSKEnvelope.swift
index c43949734..6dfca1c97 100644
--- a/SignalServiceKit/src/Protos/ProtoWrappers/SSKEnvelope.swift
+++ b/SignalServiceKit/src/Protos/ProtoWrappers/SSKEnvelope.swift
@@ -7,7 +7,7 @@ import Foundation
 @objc
 public class SSKEnvelope: NSObject {
 
-    enum EnvelopeError: Error {
+    public enum EnvelopeError: Error {
         case invalidProtobuf(description: String)
     }