diff --git a/Sources/mas/Commands/Install.swift b/Sources/mas/Commands/Install.swift
index 88c2688..1ba12b0 100644
--- a/Sources/mas/Commands/Install.swift
+++ b/Sources/mas/Commands/Install.swift
@@ -29,8 +29,8 @@ extension Mas {
         func run(appLibrary: AppLibrary) throws {
             // Try to download applications with given identifiers and collect results
             let appIDs = appIDs.filter { appID in
-                if let product = appLibrary.installedApp(withAppID: appID), !force {
-                    printWarning("\(product.appName) is already installed")
+                if let appName = appLibrary.installedApps(withAppID: appID).first?.appName, !force {
+                    printWarning("\(appName) is already installed")
                     return false
                 }
 
diff --git a/Sources/mas/Commands/Lucky.swift b/Sources/mas/Commands/Lucky.swift
index 16c7948..296dde7 100644
--- a/Sources/mas/Commands/Lucky.swift
+++ b/Sources/mas/Commands/Lucky.swift
@@ -58,8 +58,8 @@ extension Mas {
         /// - Throws: Any error that occurs while attempting to install the app.
         private func install(appID: AppID, appLibrary: AppLibrary) throws {
             // Try to download applications with given identifiers and collect results
-            if let product = appLibrary.installedApp(withAppID: appID), !force {
-                printWarning("\(product.appName) is already installed")
+            if let appName = appLibrary.installedApps(withAppID: appID).first?.appName, !force {
+                printWarning("\(appName) is already installed")
             } else {
                 do {
                     try downloadAll([appID]).wait()
diff --git a/Sources/mas/Commands/Purchase.swift b/Sources/mas/Commands/Purchase.swift
index 841d26d..58a7a48 100644
--- a/Sources/mas/Commands/Purchase.swift
+++ b/Sources/mas/Commands/Purchase.swift
@@ -26,8 +26,8 @@ extension Mas {
         func run(appLibrary: AppLibrary) throws {
             // Try to download applications with given identifiers and collect results
             let appIDs = appIDs.filter { appID in
-                if let product = appLibrary.installedApp(withAppID: appID) {
-                    printWarning("\(product.appName) has already been purchased.")
+                if let appName = appLibrary.installedApps(withAppID: appID).first?.appName {
+                    printWarning("\(appName) has already been purchased.")
                     return false
                 }
 
diff --git a/Sources/mas/Commands/Uninstall.swift b/Sources/mas/Commands/Uninstall.swift
index 632c84b..afb4b12 100644
--- a/Sources/mas/Commands/Uninstall.swift
+++ b/Sources/mas/Commands/Uninstall.swift
@@ -7,8 +7,7 @@
 //
 
 import ArgumentParser
-import CommerceKit
-import StoreFoundation
+import Foundation
 
 extension Mas {
     /// Command which uninstalls apps managed by the Mac App Store.
@@ -29,16 +28,21 @@ extension Mas {
         }
 
         func run(appLibrary: AppLibrary) throws {
-            guard let product = appLibrary.installedApp(withAppID: appID) else {
+            let installedApps = appLibrary.installedApps(withAppID: appID)
+            guard !installedApps.isEmpty else {
                 throw MASError.notInstalled
             }
 
             if dryRun {
-                printInfo("\(product.appName) \(product.bundlePath)")
+                for installedApp in installedApps {
+                    printInfo("\(installedApp.appName) \(installedApp.bundlePath)")
+                }
                 printInfo("(not removed, dry run)")
             } else {
                 do {
-                    try appLibrary.uninstallApp(app: product)
+                    for installedApp in installedApps {
+                        try appLibrary.uninstallApp(app: installedApp)
+                    }
                 } catch {
                     throw MASError.uninstallFailed
                 }
diff --git a/Sources/mas/Commands/Upgrade.swift b/Sources/mas/Commands/Upgrade.swift
index 4b3740b..83c4788 100644
--- a/Sources/mas/Commands/Upgrade.swift
+++ b/Sources/mas/Commands/Upgrade.swift
@@ -58,14 +58,14 @@ extension Mas {
             let apps =
                 appIDs.isEmpty
                 ? appLibrary.installedApps
-                : appIDs.compactMap { appID in
+                : appIDs.flatMap { appID in
                     if let appID = AppID(appID) {
-                        // argument is an AppID, lookup app by id using argument
-                        return appLibrary.installedApp(withAppID: appID)
+                        // argument is an AppID, lookup apps by id using argument
+                        return appLibrary.installedApps(withAppID: appID)
                     }
 
-                    // argument is not an AppID, lookup app by name using argument
-                    return appLibrary.installedApp(named: appID)
+                    // argument is not an AppID, lookup apps by name using argument
+                    return appLibrary.installedApps(named: appID)
                 }
 
             let promises = apps.map { installedApp in
diff --git a/Sources/mas/Controllers/AppLibrary.swift b/Sources/mas/Controllers/AppLibrary.swift
index d05e180..9bcebc7 100644
--- a/Sources/mas/Controllers/AppLibrary.swift
+++ b/Sources/mas/Controllers/AppLibrary.swift
@@ -22,20 +22,20 @@ protocol AppLibrary {
 
 /// Common logic
 extension AppLibrary {
-    /// Finds an app for appID.
+    /// Finds all installed instances of apps whose app ID is `appID`.
     ///
-    /// - Parameter appID: app ID for app.
-    /// - Returns: SoftwareProduct of app if found; nil otherwise.
-    func installedApp(withAppID appID: AppID) -> SoftwareProduct? {
+    /// - Parameter appID: app ID for app(s).
+    /// - Returns: [SoftwareProduct] of matching apps.
+    func installedApps(withAppID appID: AppID) -> [SoftwareProduct] {
         let appID = NSNumber(value: appID)
-        return installedApps.first { $0.itemIdentifier == appID }
+        return installedApps.filter { $0.itemIdentifier == appID }
     }
 
-    /// Finds an app by name.
+    /// Finds all installed instances of apps whose name is `appName`.
     ///
-    /// - Parameter appName: Full title of an app.
-    /// - Returns: Software Product of app if found; nil otherwise.
-    func installedApp(named appName: String) -> SoftwareProduct? {
-        installedApps.first { $0.appName == appName }
+    /// - Parameter appName: Full name of app(s).
+    /// - Returns: [SoftwareProduct] of matching apps.
+    func installedApps(named appName: String) -> [SoftwareProduct] {
+        installedApps.filter { $0.appName == appName }
     }
 }