diff --git a/collects/drscheme/private/eval.ss b/collects/drscheme/private/eval.ss
index 74848d4753..6eedc4e2dc 100644
--- a/collects/drscheme/private/eval.ss
+++ b/collects/drscheme/private/eval.ss
@@ -19,15 +19,18 @@
     (import [prefix drscheme:language-configuration: drscheme:language-configuration/internal^]
             [prefix drscheme:rep: drscheme:rep^]
             [prefix drscheme:init: drscheme:init^]
-            [prefix drscheme:language: drscheme:language^])
+            [prefix drscheme:language: drscheme:language^]
+            [prefix drscheme:unit: drscheme:unit^])
     (export drscheme:eval^)
     
     (define (editor->port-name txt)
       (let* ([b (box #f)]
              [n (send txt get-filename b)])
         (cond
-          [(or (unbox b) (not n)) 
-           'unknown]
+          [(or (unbox b) (not n))
+           (if (is-a? txt drscheme:unit:definitions-text<%>)
+               (send txt get-port-name-identifier)
+               'unknown)]
           [else n])))
     
     (define (traverse-program/multiple language-settings
diff --git a/collects/drscheme/private/rep.ss b/collects/drscheme/private/rep.ss
index 24a36ed59a..22e16a3409 100644
--- a/collects/drscheme/private/rep.ss
+++ b/collects/drscheme/private/rep.ss
@@ -756,8 +756,7 @@ TODO
                                             (number? (srcloc-position loc))
                                             (number? (srcloc-span loc))))
                               (map (λ (srcloc)
-                                     (if (equal? (normal-case-path (normalize-path (send definitions-text get-filename)))
-                                                 (normal-case-path (normalize-path (srcloc-source srcloc))))
+                                     (if (send definitions-text port-name-matches? (srcloc-source srcloc))
                                          (make-srcloc definitions-text
                                                       (srcloc-line srcloc)
                                                       (srcloc-column srcloc)
diff --git a/collects/drscheme/private/unit.ss b/collects/drscheme/private/unit.ss
index a0b627d48b..4c048635a7 100644
--- a/collects/drscheme/private/unit.ss
+++ b/collects/drscheme/private/unit.ss
@@ -92,7 +92,9 @@ module browser threading seems wrong.
         get-tab
         get-next-settings
         after-set-next-settings
-        set-needs-execution-message))
+        set-needs-execution-message
+        get-port-name-identifier
+        port-name-matches?))
     
     (define-struct teachpack-callbacks 
       (get-names   ;; settings -> (listof string)
@@ -403,6 +405,20 @@ module browser threading seems wrong.
           (define/public (get-tab) tab)
           (define/public (set-tab t) (set! tab t))
           
+          (define port-name-identifier #f)
+          (define/public (get-port-name-identifier)
+            (unless port-name-identifier
+              (set! port-name-identifier (gensym 'unsaved-editor)))
+            port-name-identifier)
+          (define/public (port-name-matches? id)
+            (let ([filename (get-filename)])
+              (or (and (path? id)
+                       (path? filename)
+                       (equal? (normal-case-path (normalize-path (get-filename)))
+                               (normal-case-path (normalize-path id))))
+                  (and (symbol? port-name-identifier)
+                       (equal? port-name-identifier id)))))
+          
           (inherit get-surrogate set-surrogate)
           (define/public (set-current-mode mode)
             (let ([surrogate (drscheme:modes:mode-surrogate mode)])