diff --git a/Sources/SourceKitLSP/SourceKitLSPServer.swift b/Sources/SourceKitLSP/SourceKitLSPServer.swift
index a684d6d38..7372f7d69 100644
--- a/Sources/SourceKitLSP/SourceKitLSPServer.swift
+++ b/Sources/SourceKitLSP/SourceKitLSPServer.swift
@@ -519,7 +519,7 @@ package actor SourceKitLSPServer {
         syncKind = .incremental
       }
       guard syncKind == .incremental else {
-        fatalError("non-incremental update not implemented")
+        throw ResponseError.internalError("non-incremental update not implemented")
       }
 
       await service.clientInitialized(InitializedNotification())