diff --git a/AltStore/Operations/Errors/SourceError.swift b/AltStore/Operations/Errors/SourceError.swift
index bbf0110d..648b7e3d 100644
--- a/AltStore/Operations/Errors/SourceError.swift
+++ b/AltStore/Operations/Errors/SourceError.swift
@@ -24,6 +24,9 @@ extension SourceError
         
         case missingPermissionUsageDescription
         case missingScreenshotSize
+        
+        case marketplaceAppsNotSupported = 101
+        case marketplaceAppsRequired
     }
     
     static func unsupported(_ source: Source) -> SourceError { SourceError(code: .unsupported, source: source) }
@@ -41,6 +44,14 @@ extension SourceError
     static func missingScreenshotSize(for screenshot: AppScreenshot, source: Source) -> SourceError {
         SourceError(code: .missingScreenshotSize, source: source, app: screenshot.app, screenshotURL: screenshot.imageURL)
     }
+    
+    static func marketplaceAppsNotSupported(source: Source) -> SourceError {
+        return SourceError(code: .marketplaceAppsNotSupported, source: source)
+    }
+    
+    static func marketplaceAppsRequired(source: Source) -> SourceError {
+        return SourceError(code: .marketplaceAppsRequired, source: source)
+    }
 }
 
 struct SourceError: ALTLocalizedError
@@ -128,6 +139,14 @@ struct SourceError: ALTLocalizedError
             
             let failureReason = baseMessage + ": \(screenshotURL.absoluteString)"
             return failureReason
+            
+        case .marketplaceAppsNotSupported:
+            let failureReason = String(format: NSLocalizedString("The source “%@” contains notarized apps, which are not supported by this version of AltStore.", comment: ""), self.$source.name)
+            return failureReason
+            
+        case .marketplaceAppsRequired:
+            let failureReason = String(format: NSLocalizedString("The source “%@” contains non-marketplace apps, which are not supported by this version of AltStore.", comment: ""), self.$source.name)
+            return failureReason
         }
     }
     
@@ -166,6 +185,10 @@ struct SourceError: ALTLocalizedError
             let recoverySuggestion = NSLocalizedString("Please remove the existing source in order to add this one.", comment: "")
             return recoverySuggestion
             
+        case .marketplaceAppsRequired:
+            let failureReason = String(format: NSLocalizedString("AltStore can only install marketplace apps that have been notarized by Apple.", comment: ""), self.$source.name)
+            return failureReason
+            
         default: return nil
         }
     }
diff --git a/AltStore/Operations/FetchSourceOperation.swift b/AltStore/Operations/FetchSourceOperation.swift
index 1eacc0eb..52866172 100644
--- a/AltStore/Operations/FetchSourceOperation.swift
+++ b/AltStore/Operations/FetchSourceOperation.swift
@@ -226,6 +226,12 @@ private extension FetchSourceOperation
                 // All iPad screenshots MUST have an explicit size.
                 guard screenshot.size != nil else { throw SourceError.missingScreenshotSize(for: screenshot, source: source) }
             }
+            
+            #if MARKETPLACE
+            guard app.marketplaceID != nil else { throw SourceError.marketplaceAppsRequired(source: source) }
+            #else
+            guard app.marketplaceID == nil else { throw SourceError.marketplaceAppsNotSupported(source: source) }
+            #endif
         }
         
         if let previousSourceID = self.$source.identifier
diff --git a/AltStoreCore/Model/AltStore.xcdatamodeld/AltStore 16.xcdatamodel/contents b/AltStoreCore/Model/AltStore.xcdatamodeld/AltStore 16.xcdatamodel/contents
index e02a449e..f6b5f36c 100644
--- a/AltStoreCore/Model/AltStore.xcdatamodeld/AltStore 16.xcdatamodel/contents	
+++ b/AltStoreCore/Model/AltStore.xcdatamodeld/AltStore 16.xcdatamodel/contents	
@@ -250,6 +250,7 @@
         <attribute name="isPledged" attributeType="Boolean" defaultValueString="NO" usesScalarValueType="YES"/>
         <attribute name="isPledgeRequired" attributeType="Boolean" defaultValueString="NO" usesScalarValueType="YES"/>
         <attribute name="localizedDescription" attributeType="String"/>
+        <attribute name="marketplaceID" optional="YES" attributeType="String"/>
         <attribute name="name" attributeType="String"/>
         <attribute name="pledgeAmount" optional="YES" attributeType="Decimal"/>
         <attribute name="pledgeCurrency" optional="YES" attributeType="String"/>
diff --git a/AltStoreCore/Model/StoreApp.swift b/AltStoreCore/Model/StoreApp.swift
index 2f374e79..005b271b 100644
--- a/AltStoreCore/Model/StoreApp.swift
+++ b/AltStoreCore/Model/StoreApp.swift
@@ -152,6 +152,9 @@ public class StoreApp: NSManagedObject, Decodable, Fetchable
     @NSManaged public private(set) var tintColor: UIColor?
     @NSManaged public private(set) var isBeta: Bool
     
+    // Required for Marketplace apps.
+    @NSManaged public private(set) var marketplaceID: String?
+
     @NSManaged public var isPledged: Bool
     @NSManaged public private(set) var isPledgeRequired: Bool
     @NSManaged public private(set) var isHiddenWithoutPledge: Bool
@@ -275,6 +278,7 @@ public class StoreApp: NSManagedObject, Decodable, Fetchable
     {
         case name
         case bundleIdentifier
+        case marketplaceID
         case developerName
         case localizedDescription
         case iconURL
@@ -345,6 +349,8 @@ public class StoreApp: NSManagedObject, Decodable, Fetchable
                     } else {
                         throw DecodingError.dataCorruptedError(forKey: .downloadURL, in: container, debugDescription: "E downloadURL:String or downloadURLs:[[Platform:URL]] key required.")
                     }
+            // Required for Marketplace apps, but we'll verify later.
+            self.marketplaceID = try container.decodeIfPresent(String.self, forKey: .marketplaceID)
 
 //                 else {
 //                throw DecodingError.dataCorruptedError(forKey: .downloadURL, in: container, debugDescription: "E downloadURL:String or downloadURLs:[[Platform:URL]] key required.")