diff --git a/prototype/DoubtTests/DiffTests.swift b/prototype/DoubtTests/DiffTests.swift
index 554d0eb05..20348fbc1 100644
--- a/prototype/DoubtTests/DiffTests.swift
+++ b/prototype/DoubtTests/DiffTests.swift
@@ -45,5 +45,6 @@ private func SES(a: [Term], _ b: [Term]) -> [Diff] {
 }
 
 
+import Assertions
 @testable import Doubt
 import XCTest