diff --git a/Sources/SKCore/BuildServerBuildSystem.swift b/Sources/SKCore/BuildServerBuildSystem.swift
index fc35d488..a6c9bcfe 100644
--- a/Sources/SKCore/BuildServerBuildSystem.swift
+++ b/Sources/SKCore/BuildServerBuildSystem.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -171,7 +171,10 @@ extension BuildServerBuildSystem: BuildSystem {
 
   public func settings(for uri: DocumentURI, _ language: Language) -> FileBuildSettings? {
     if let response = try? self.buildServer?.sendSync(SourceKitOptions(uri: uri)) {
-      return FileBuildSettings(compilerArguments: response.options, workingDirectory: response.workingDirectory)
+      return FileBuildSettings(
+        compilerArguments: response.options,
+        workingDirectory: response.workingDirectory,
+        language: language)
     }
     return nil
   }
diff --git a/Sources/SKCore/CompilationDatabaseBuildSystem.swift b/Sources/SKCore/CompilationDatabaseBuildSystem.swift
index ff481e06..4ba5d618 100644
--- a/Sources/SKCore/CompilationDatabaseBuildSystem.swift
+++ b/Sources/SKCore/CompilationDatabaseBuildSystem.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -68,8 +68,8 @@ extension CompilationDatabaseBuildSystem: BuildSystem {
           let cmd = db[url].first else { return nil }
     return FileBuildSettings(
       compilerArguments: Array(cmd.commandLine.dropFirst()),
-      workingDirectory: cmd.directory
-    )
+      workingDirectory: cmd.directory,
+      language: language)
   }
 
   public func toolchain(for: DocumentURI, _ language: Language) -> Toolchain? { return nil }
diff --git a/Sources/SKCore/FallbackBuildSystem.swift b/Sources/SKCore/FallbackBuildSystem.swift
index 134a3c4f..84beda83 100644
--- a/Sources/SKCore/FallbackBuildSystem.swift
+++ b/Sources/SKCore/FallbackBuildSystem.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -79,7 +79,7 @@ public final class FallbackBuildSystem: BuildSystem {
       ]
     }
     args.append(file)
-    return FileBuildSettings(compilerArguments: args)
+    return FileBuildSettings(compilerArguments: args, language: .swift)
   }
 
   func settingsClang(_ file: String, _ language: Language) -> FileBuildSettings {
@@ -91,6 +91,6 @@ public final class FallbackBuildSystem: BuildSystem {
       ]
     }
     args.append(file)
-    return FileBuildSettings(compilerArguments: args)
+    return FileBuildSettings(compilerArguments: args, language: language)
   }
 }
diff --git a/Sources/SKCore/FileBuildSettings.swift b/Sources/SKCore/FileBuildSettings.swift
index 1d505227..2f84e5d2 100644
--- a/Sources/SKCore/FileBuildSettings.swift
+++ b/Sources/SKCore/FileBuildSettings.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -10,6 +10,8 @@
 //
 //===----------------------------------------------------------------------===//
 
+import LanguageServerProtocol
+
 /// Build settings for a single file.
 ///
 /// Encapsulates all the settings needed to compile a single file, including the compiler arguments
@@ -22,11 +24,16 @@ public struct FileBuildSettings: Equatable {
   /// The working directory to resolve any relative paths in `compilerArguments`.
   public var workingDirectory: String? = nil
 
+  /// The language of this file.
+  public var language: Language
+
   public init(
     compilerArguments: [String],
-    workingDirectory: String? = nil)
+    workingDirectory: String? = nil,
+    language: Language)
   {
     self.compilerArguments = compilerArguments
     self.workingDirectory = workingDirectory
+    self.language = language
   }
 }
diff --git a/Sources/SKSwiftPMWorkspace/SwiftPMWorkspace.swift b/Sources/SKSwiftPMWorkspace/SwiftPMWorkspace.swift
index f3cdab9a..6a5d77e5 100644
--- a/Sources/SKSwiftPMWorkspace/SwiftPMWorkspace.swift
+++ b/Sources/SKSwiftPMWorkspace/SwiftPMWorkspace.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2018 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -294,7 +294,7 @@ extension SwiftPMWorkspace {
     func impl(_ path: AbsolutePath) -> FileBuildSettings? {
       for package in packageGraph.packages where path == package.manifest.path {
         let compilerArgs = workspace.interpreterFlags(for: package.path) + [path.pathString]
-        return FileBuildSettings(compilerArguments: compilerArgs)
+        return FileBuildSettings(compilerArguments: compilerArgs, language: .swift)
       }
       return nil
     }
@@ -354,7 +354,8 @@ extension SwiftPMWorkspace {
 
     return FileBuildSettings(
       compilerArguments: args,
-      workingDirectory: workspacePath.pathString)
+      workingDirectory: workspacePath.pathString,
+      language: .swift)
   }
 
   /// Retrieve settings for the given C-family language file, which is part of a known target build
@@ -416,7 +417,8 @@ extension SwiftPMWorkspace {
 
     return FileBuildSettings(
       compilerArguments: args,
-      workingDirectory: workspacePath.pathString)
+      workingDirectory: workspacePath.pathString,
+      language: language)
   }
 }
 
diff --git a/Tests/SourceKitTests/BuildSystemTests.swift b/Tests/SourceKitTests/BuildSystemTests.swift
index 96d2fb96..27efd8e1 100644
--- a/Tests/SourceKitTests/BuildSystemTests.swift
+++ b/Tests/SourceKitTests/BuildSystemTests.swift
@@ -2,7 +2,7 @@
 //
 // This source file is part of the Swift.org open source project
 //
-// Copyright (c) 2014 - 2019 Apple Inc. and the Swift project authors
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
 // Licensed under Apache License v2.0 with Runtime Library Exception
 //
 // See https://swift.org/LICENSE.txt for license information
@@ -132,7 +132,8 @@ final class BuildSystemTests: XCTestCase {
     }
     """
 
-    buildSystem.buildSettingsByFile[DocumentURI(url)] = FileBuildSettings(compilerArguments: args)
+    buildSystem.buildSettingsByFile[DocumentURI(url)] =
+      FileBuildSettings(compilerArguments: args, language: .objective_c)
 
     sk.allowUnexpectedNotification = false
 
@@ -148,7 +149,8 @@ final class BuildSystemTests: XCTestCase {
 
     // Modify the build settings and inform the delegate.
     // This should trigger a new publish diagnostics and we should no longer have errors.
-    buildSystem.buildSettingsByFile[DocumentURI(url)] = FileBuildSettings(compilerArguments: args +  ["-DFOO"])
+    buildSystem.buildSettingsByFile[DocumentURI(url)] = 
+      FileBuildSettings(compilerArguments: args +  ["-DFOO"], language: .objective_c)
     testServer.server?.fileBuildSettingsChanged([DocumentURI(url)])
 
     let expectation = XCTestExpectation(description: "refresh")
@@ -168,7 +170,8 @@ final class BuildSystemTests: XCTestCase {
     let url = URL(fileURLWithPath: "/a.swift")
     let args = FallbackBuildSystem().settings(for: DocumentURI(url), .swift)!.compilerArguments
 
-    buildSystem.buildSettingsByFile[DocumentURI(url)] = FileBuildSettings(compilerArguments: args)
+    buildSystem.buildSettingsByFile[DocumentURI(url)] =
+      FileBuildSettings(compilerArguments: args, language: .swift)
 
     let text = """
     #if FOO
@@ -196,7 +199,8 @@ final class BuildSystemTests: XCTestCase {
 
     // Modify the build settings and inform the delegate.
     // This should trigger a new publish diagnostics and we should no longer have errors.
-    buildSystem.buildSettingsByFile[DocumentURI(url)] = FileBuildSettings(compilerArguments: args + ["-DFOO"])
+    buildSystem.buildSettingsByFile[DocumentURI(url)] =
+      FileBuildSettings(compilerArguments: args + ["-DFOO"], language: .swift)
 
     let expectation = XCTestExpectation(description: "refresh")
     expectation.expectedFulfillmentCount = 2