diff --git a/prototype/Doubt.xcworkspace/contents.xcworkspacedata b/prototype/Doubt.xcworkspace/contents.xcworkspacedata
index e9a97cf75..13755c746 100644
--- a/prototype/Doubt.xcworkspace/contents.xcworkspacedata
+++ b/prototype/Doubt.xcworkspace/contents.xcworkspacedata
@@ -7,6 +7,9 @@
    <FileRef
       location = "group:External/Assertions/Assertions.xcodeproj">
    </FileRef>
+   <FileRef
+      location = "group:External/SwiftCheck/SwiftCheck.xcodeproj">
+   </FileRef>
    <FileRef
       location = "group:External/Stream/Stream.xcodeproj">
    </FileRef>