diff --git a/Mist/Extensions/Sequence+Extension.swift b/Mist/Extensions/Sequence+Extension.swift
index 53a0dfb..dca8fb4 100644
--- a/Mist/Extensions/Sequence+Extension.swift
+++ b/Mist/Extensions/Sequence+Extension.swift
@@ -30,7 +30,12 @@ extension Sequence where Iterator.Element == [String: Any] {
     /// - Returns: A JSON string representation.
     func jsonString() throws -> String {
         let data: Data = try JSONSerialization.data(withJSONObject: self, options: [.prettyPrinted, .sortedKeys])
-        return String(decoding: data, as: UTF8.self)
+
+        guard let string: String = String(data: data, encoding: .utf8) else {
+            throw MistError.invalidData
+        }
+
+        return string
     }
 
     /// Provides a Property List string representation.
@@ -40,7 +45,12 @@ extension Sequence where Iterator.Element == [String: Any] {
     /// - Returns: A Property List string representation.
     func propertyListString() throws -> String {
         let data: Data = try PropertyListSerialization.data(fromPropertyList: self, format: .xml, options: .bitWidth)
-        return String(decoding: data, as: UTF8.self)
+
+        guard let string: String = String(data: data, encoding: .utf8) else {
+            throw MistError.invalidData
+        }
+
+        return string
     }
 
     /// Provides a YAML string representation.
diff --git a/Mist/Views/Activity/ActivityView.swift b/Mist/Views/Activity/ActivityView.swift
index 7e69183..a5e6588 100644
--- a/Mist/Views/Activity/ActivityView.swift
+++ b/Mist/Views/Activity/ActivityView.swift
@@ -178,7 +178,7 @@ struct ActivityView: View {
     }
 
     private func checkForUserCancellation(_ failure: Error) -> Bool {
-        if failure as? CancellationError != nil {
+        if failure is CancellationError {
             return true
         }
 
diff --git a/Mist/Views/Refresh/RefreshView.swift b/Mist/Views/Refresh/RefreshView.swift
index bc50be6..6746032 100644
--- a/Mist/Views/Refresh/RefreshView.swift
+++ b/Mist/Views/Refresh/RefreshView.swift
@@ -242,7 +242,7 @@ struct RefreshView: View {
                 var value: [String: Any] = value as? [String: Any],
                 let date: Date = value["PostDate"] as? Date,
                 let extendedMetaInfo: [String: Any] = value["ExtendedMetaInfo"] as? [String: Any],
-                extendedMetaInfo["InstallAssistantPackageIdentifiers"] as? [String: Any] != nil,
+                extendedMetaInfo["InstallAssistantPackageIdentifiers"] is [String: Any],
                 let distributions: [String: Any] = value["Distributions"] as? [String: Any],
                 let distributionURL: String = distributions["English"] as? String,
                 let url: URL = URL(string: distributionURL) else {