diff --git a/collects/tests/typed-scheme/succeed/somesystempath.rkt b/collects/tests/typed-scheme/succeed/somesystempath.rkt
new file mode 100644
index 0000000000..1ad85b21ac
--- /dev/null
+++ b/collects/tests/typed-scheme/succeed/somesystempath.rkt
@@ -0,0 +1,27 @@
+#lang typed/racket
+
+(: unix-path SomeSystemPath)
+(define unix-path (string->some-system-path "file.rkt" 'unix))
+
+(: windows-path SomeSystemPath)
+(define windows-path (string->some-system-path "file.rkt" 'windows))
+
+(for: ((p : SomeSystemPath (list unix-path windows-path)))
+ (let ((long-path (build-path p 'up 'same p)))
+   (unless (path-for-some-system? p)
+    (error "Predicate failed"))
+   (explode-path long-path)
+   
+   (filename-extension p)
+   (path-only long-path)
+   (some-system-path->string long-path)
+   
+   ))
+
+
+(when (equal? 'unix (system-path-convention-type))
+ (find-relative-path (simplify-path (path->complete-path "foo")) (simplify-path (path->complete-path "foo/foo/foo"))))
+
+
+
+
diff --git a/collects/typed-scheme/base-env/base-env.rkt b/collects/typed-scheme/base-env/base-env.rkt
index 2d5d294161..96ef4b2495 100644
--- a/collects/typed-scheme/base-env/base-env.rkt
+++ b/collects/typed-scheme/base-env/base-env.rkt
@@ -394,7 +394,7 @@
 [string->path (-> -String -Path)]
 
 
-[build-path ((list -Pathlike*) -Pathlike* . ->* . -Path)]
+[build-path ((list -SomeSystemPathlike*) -SomeSystemPathlike* . ->* . -Path)]
 [with-input-from-file
  (-poly (a) (->key -Pathlike (-> a) #:mode (one-of/c 'binary 'text) #f a))]
 [with-output-to-file
@@ -750,6 +750,7 @@
 [object-name (Univ . -> . Univ)]
 
 [path? (make-pred-ty -Path)]
+[path-for-some-system? (make-pred-ty -SomeSystemPath)]
 
 ;; scheme/function
 [const (-poly (a) (-> a (->* '() Univ a)))]
@@ -843,16 +844,23 @@
 
 ;; scheme/path
 
-[explode-path (-Pathlike . -> . (-lst (Un -Path (-val 'up) (-val 'same))))]
-[find-relative-path (-Pathlike -Pathlike . -> . -Path)]
+[explode-path (-SomeSystemPathlike . -> . (-lst (Un -SomeSystemPath (-val 'up) (-val 'same))))]
+[find-relative-path (-SomeSystemPathlike -SomeSystemPathlike . -> . -SomeSystemPath)]
 [simple-form-path (-Pathlike . -> . -Path)]
 [normalize-path (cl->* (-Pathlike [-Pathlike] . ->opt . -Path))]
-[filename-extension (-Pathlike . -> . (-opt -Bytes))]
+[filename-extension (-SomeSystemPathlike . -> . (-opt -Bytes))]
 [file-name-from-path (-Pathlike . -> . (-opt -Path))]
-[path-only (-Pathlike . -> . (-opt -Path))]
-[some-system-path->string (-Path . -> . -String)]
+[path-only (-SomeSystemPathlike . -> . (-opt -Path))]
+[some-system-path->string (-SomeSystemPath . -> . -String)]
 [string->some-system-path 
- (-String (Un (-val 'unix) (-val 'windows)) . -> . -Path)]
+ (-String (Un (-val 'unix) (-val 'windows)) . -> . -SomeSystemPath)]
+
+[simplify-path (-SomeSystemPathlike [B] . ->opt . -SomeSystemPath)]
+[path->complete-path
+ (cl->* (-> -Pathlike -Path)
+        (-> -SomeSystemPathlike -SomeSystemPathlike -SomeSystemPath))]
+[system-path-convention-type (-> (Un (-val 'unix) (-val 'windows)))]
+
 
 ;; scheme/file
 [fold-files 
diff --git a/collects/typed-scheme/base-env/base-types.rkt b/collects/typed-scheme/base-env/base-types.rkt
index 1f63fe699b..9f7a88b959 100644
--- a/collects/typed-scheme/base-env/base-types.rkt
+++ b/collects/typed-scheme/base-env/base-types.rkt
@@ -77,6 +77,7 @@
 [Any Univ]
 [Port -Port]
 [Path -Path]
+[SomeSystemPath -SomeSystemPath]
 [Path-String -Pathlike]
 [Regexp -Regexp]
 [PRegexp -PRegexp]
diff --git a/collects/typed-scheme/types/abbrev.rkt b/collects/typed-scheme/types/abbrev.rkt
index 460818bef4..b9778e438d 100644
--- a/collects/typed-scheme/types/abbrev.rkt
+++ b/collects/typed-scheme/types/abbrev.rkt
@@ -143,6 +143,10 @@
 (define -Prompt-Tag (make-Base 'Prompt-Tag #'continuation-prompt-tag? continuation-prompt-tag? #'-Prompt-Tag))
 (define -Cont-Mark-Set (make-Base 'Continuation-Mark-Set #'continuation-mark-set? continuation-mark-set? #'-Cont-Mark-Set))
 (define -Path (make-Base 'Path #'path? path? #'-Path))
+(define -OtherSystemPath (make-Base 'OtherSystemPath
+                           #'(and/c path-for-some-system? (not/c path?))
+                             (conjoin path-for-some-system? (negate path?))
+                             #'-OtherSystemPath))
 (define -Namespace (make-Base 'Namespace #'namespace? namespace? #'-Namespace))
 (define -Output-Port (make-Base 'Output-Port #'output-port? output-port? #'-Output-Port))
 (define -Input-Port (make-Base 'Input-Port #'input-port? input-port? #'-Input-Port))
@@ -159,8 +163,11 @@
 
 (define -Port (*Un -Output-Port -Input-Port))
 
+(define -SomeSystemPath (*Un -Path -OtherSystemPath))
 (define -Pathlike (*Un -String -Path))
-(define -Pathlike* (*Un -String -Path (-val 'up) (-val 'same)))
+(define -SomeSystemPathlike (*Un -String -SomeSystemPath))
+;(define -Pathlike* (*Un -String -Path (-val 'up) (-val 'same)))
+(define -SomeSystemPathlike* (*Un -String -SomeSystemPath(-val 'up) (-val 'same)))
 (define -Pattern (*Un -Bytes -Regexp -PRegexp -Byte-Regexp -Byte-PRegexp -String))
 
 (define -top (make-Top))