diff --git a/Sources/ProjectSpec/Project.swift b/Sources/ProjectSpec/Project.swift
index 201cd0f8..57bdeaf2 100644
--- a/Sources/ProjectSpec/Project.swift
+++ b/Sources/ProjectSpec/Project.swift
@@ -170,6 +170,14 @@ extension Project {
     public init(basePath: Path = "", jsonDictionary: JSONDictionary) throws {
         self.basePath = basePath
 
+        let validKeys = Set(["name", "settings", "settingGroups", "settingPresets", "configs", "targets", "aggregateTargets", "projectReferences", "schemes", "breakpoints", "fileGroups", "configFiles", "attributes", "breakpoints", "packages", "localPackages", "options", "targetTemplates", "include", "templates", "schemeTemplates"])
+
+        for key in jsonDictionary.keys {
+            if !validKeys.contains(key) {
+                throw SpecValidationError(errors: [.unknownDictionaryKey(key)])
+            }
+        }
+
         let jsonDictionary = Project.resolveProject(jsonDictionary: jsonDictionary)
 
         name = try jsonDictionary.json(atKeyPath: "name")
diff --git a/Sources/ProjectSpec/SpecValidationError.swift b/Sources/ProjectSpec/SpecValidationError.swift
index 6e93de0e..cb9eac11 100644
--- a/Sources/ProjectSpec/SpecValidationError.swift
+++ b/Sources/ProjectSpec/SpecValidationError.swift
@@ -42,6 +42,7 @@ public struct SpecValidationError: Error, CustomStringConvertible {
         case multipleDefaultTestPlans
         case duplicateDependencies(target: String, dependencyReference: String)
         case invalidPluginPackageReference(plugin: String, package: String)
+        case unknownDictionaryKey(String)
 
         public var description: String {
             switch self {
@@ -109,6 +110,8 @@ public struct SpecValidationError: Error, CustomStringConvertible {
                  return "Target \(target.quoted) has the dependency \(dependencyReference.quoted) multiple times"
             case let .invalidPluginPackageReference(plugin, package):
                 return "Plugin \(plugin) has invalid package reference \(package)"
+            case let .unknownDictionaryKey(key):
+                return "Unknown key \(key)"
             }
         }
     }