diff --git a/basis/alien/libraries/libraries.factor b/basis/alien/libraries/libraries.factor
index e24105651a..b8466e023a 100755
--- a/basis/alien/libraries/libraries.factor
+++ b/basis/alien/libraries/libraries.factor
@@ -2,39 +2,37 @@
 ! See http://factorcode.org/license.txt for BSD license.
 USING: accessors alien alien.strings assocs io.backend
 kernel namespaces destructors sequences strings
-system io.pathnames fry ;
+system io.pathnames fry combinators vocabs.loader ;
 IN: alien.libraries
 
-ERROR: unknown-dlsym-platform ;
-<< {
-    { [ os windows? ] [ "alien.libraries.windows" ] }
-    { [ os unix? ] [ "alien.libraries.unix" ] }
-    [ unknown-dlsym-platform ]
-} cond use-vocab >>
-
 : dlopen ( path -- dll ) native-string>alien (dlopen) ;
 
 : dlsym ( name dll -- alien ) [ string>symbol ] dip (dlsym) ;
 
 : dlsym-raw ( name dll -- alien ) [ string>symbol ] dip (dlsym-raw) ;
 
-: dlerror ( -- message/f ) (dlerror) ;
+HOOK: dlerror os ( -- message/f )
 
 SYMBOL: libraries
 
 libraries [ H{ } clone ] initialize
 
-TUPLE: library { path string } { abi abi initial: cdecl } dll ;
+TUPLE: library { path string } { abi abi initial: cdecl } dll dlerror ;
 
 ERROR: no-library name ;
 
 : library ( name -- library ) libraries get at ;
 
 : <library> ( path abi -- library )
-    over dup [ dlopen ] when \ library boa ;
+    over dup
+    [ dlopen dup dll-valid? [ f ] [ dlerror ] if ] [ f ] if
+    \ library boa ;
+
+: library-dll ( library -- dll )
+    dup [ dll>> ] when ;
 
 : load-library ( name -- dll )
-    library dup [ dll>> ] when ;
+    library library-dll ;
 
 M: dll dispose dlclose ;
 
@@ -70,17 +68,9 @@ deploy-libraries [ V{ } clone ] initialize
     [ deploy-libraries get 2dup member? [ 2drop ] [ push ] if ]
     [ no-library ] if ;
 
-<PRIVATE
-
 HOOK: >deployed-library-path os ( path -- path' )
 
-M: windows >deployed-library-path
-    file-name ;
-
-M: unix >deployed-library-path
-    file-name "$ORIGIN" prepend-path ;
-
-M: macosx >deployed-library-path
-    file-name "@executable_path/../Frameworks" prepend-path ;
-
-PRIVATE>
+<< {
+    { [ os windows? ] [ "alien.libraries.windows" ] }
+    { [ os unix? ] [ "alien.libraries.unix" ] }
+} cond require >>
diff --git a/basis/alien/libraries/unix/unix.factor b/basis/alien/libraries/unix/unix.factor
index 8db779d013..84cea56041 100644
--- a/basis/alien/libraries/unix/unix.factor
+++ b/basis/alien/libraries/unix/unix.factor
@@ -1,5 +1,15 @@
-USING: alien.c-types alien.syntax io.encodings.utf8 ;
+USING: alien.c-types alien.libraries alien.syntax io.encodings.utf8
+io.pathnames system ;
 IN: alien.libraries.unix
 
 FUNCTION-ALIAS: (dlerror)
-    c-string[utf8] dlerror ( ) ;
+    c-string dlerror ( ) ;
+
+M: unix dlerror (dlerror) ;
+
+M: unix >deployed-library-path
+    file-name "$ORIGIN" prepend-path ;
+
+M: macosx >deployed-library-path
+    file-name "@executable_path/../Frameworks" prepend-path ;
+
diff --git a/basis/alien/libraries/windows/windows.factor b/basis/alien/libraries/windows/windows.factor
index 9a595c8a09..249bcff57a 100644
--- a/basis/alien/libraries/windows/windows.factor
+++ b/basis/alien/libraries/windows/windows.factor
@@ -1,5 +1,8 @@
-USING: windows.errors ;
+USING: alien.libraries io.pathnames system windows.errors ;
 IN: alien.libraries.windows
 
-: (dlerror) ( -- message )
+M: windows >deployed-library-path
+    file-name ;
+
+M: windows dlerror ( -- message )
     win32-error-string ;
diff --git a/basis/compiler/cfg/builder/alien/alien.factor b/basis/compiler/cfg/builder/alien/alien.factor
index 114d1deb3e..8c1a213fb8 100644
--- a/basis/compiler/cfg/builder/alien/alien.factor
+++ b/basis/compiler/cfg/builder/alien/alien.factor
@@ -67,11 +67,17 @@ M: string dlsym-valid? dlsym ;
 
 M: array dlsym-valid? '[ _ dlsym ] any? ;
 
-: check-dlsym ( symbols dll -- )
-    dup dll-valid? [
-        dupd dlsym-valid?
-        [ drop ] [ dlerror cfg get word>> no-such-symbol ] if
-    ] [ dll-path "" cfg get word>> no-such-library drop ] if ;
+: check-dlsym ( symbols library -- )
+    {
+        { [ dup library-dll dll-valid? not ] [
+            [ library-dll dll-path ] [ dlerror>> ] bi
+            cfg get word>> no-such-library drop 
+        ] }
+        { [ 2dup library-dll dlsym-valid? not ] [
+            drop dlerror cfg get word>> no-such-symbol
+        ] }
+        [ 2drop ]
+    } cond ;
 
 : decorated-symbol ( params -- symbols )
     [ function>> ] [ parameters>> [ stack-size ] map-sum number>string ] bi
@@ -85,7 +91,7 @@ M: array dlsym-valid? '[ _ dlsym ] any? ;
 
 : caller-linkage ( params -- symbols dll )
     [ dup abi>> callee-cleanup? [ decorated-symbol ] [ function>> ] if ]
-    [ library>> load-library ]
+    [ library>> library ]
     bi 2dup check-dlsym ;
 
 : caller-return ( params -- )