diff --git a/collects/tests/mzscheme/unit.ss b/collects/tests/mzscheme/unit.ss
index e9bb664..1dd3b8d 100644
--- a/collects/tests/mzscheme/unit.ss
+++ b/collects/tests/mzscheme/unit.ss
@@ -77,6 +77,8 @@
 		  (U b))])
 	(export))))
 
+(error-test '(invoke-unit (unit (import not-defined) (export) 10) not-defined) exn:unit?)
+
 (unless (defined? 'test-global-var)
   (let ()
     (define test-global-var 5)
diff --git a/collects/tests/mzscheme/unitsig.ss b/collects/tests/mzscheme/unitsig.ss
index 7cbf23a..fe571ea 100644
--- a/collects/tests/mzscheme/unitsig.ss
+++ b/collects/tests/mzscheme/unitsig.ss
@@ -131,6 +131,9 @@
 			U)])
 	(export))))
 
+(define-signature not-defined^ (not-defined))
+(error-test '(invoke-unit/sig (unit/sig () (import not-defined^) 10) not-defined^) exn:unit?)
+
 (test #t unit/sig? (unit/sig a (import)))
 (test #t unit/sig? (unit/sig b (import) (define x 1) (define y 2)))
 (test #t unit/sig? (unit/sig a (import (i : b)) i:x))