diff --git a/Makefile b/Makefile
index a652edbcea..5e63017218 100644
--- a/Makefile
+++ b/Makefile
@@ -162,11 +162,11 @@ factor-console: $(DLL_OBJS) $(EXE_OBJS)
 		$(CFLAGS) $(CFLAGS_CONSOLE) -o factor$(EXE_SUFFIX)$(CONSOLE_EXTENSION) $(EXE_OBJS)
 
 factor-ffi-test: vm/ffi_test.o
-	$(CC) $(LIBPATH) $(CFLAGS) $(FFI_TEST_CFLAGS) $(SHARED_FLAG) -o libfactor-ffi-test$(DLL_EXTENSION) $(TEST_OBJS)
+	$(CC) $(LIBPATH) $(CFLAGS) $(FFI_TEST_CFLAGS) $(SHARED_FLAG) -o libfactor-ffi-test$(SHARED_DLL_EXTENSION) $(TEST_OBJS)
 
 clean:
 	rm -f vm/*.o
-	rm -f factor*.dll libfactor.{a,so,dylib}
+	rm -f factor*.dll libfactor.{a,so,dylib} libfactor-ffi-test.{a,so,dylib}
 
 vm/resources.o:
 	$(WINDRES) vm/factor.rs vm/resources.o
diff --git a/basis/compiler/tests/alien.factor b/basis/compiler/tests/alien.factor
index 5b3bed6554..4d7882ad08 100755
--- a/basis/compiler/tests/alien.factor
+++ b/basis/compiler/tests/alien.factor
@@ -13,7 +13,7 @@ IN: compiler.tests
     {
         { [ os winnt? ]  [ "libfactor-ffi-test.dll" ] }
         { [ os macosx? ] [ "libfactor-ffi-test.dylib" ] }
-        { [ os unix?  ]  [ "libfactor-ffi-test.a" ] }
+        { [ os unix?  ]  [ "libfactor-ffi-test.so" ] }
     } cond append-path ;
 
 "f-cdecl" libfactor-ffi-tests-path "cdecl" add-library
diff --git a/vm/Config.macosx b/vm/Config.macosx
index 6655d548b7..98d14cfdf4 100644
--- a/vm/Config.macosx
+++ b/vm/Config.macosx
@@ -4,6 +4,7 @@ CFLAGS += -fPIC
 PLAF_DLL_OBJS += vm/os-macosx.o vm/mach_signal.o
 
 DLL_EXTENSION = .dylib
+SHARED_DLL_EXTENSION = .dylib
 
 SHARED_FLAG = -dynamiclib
 
diff --git a/vm/Config.unix b/vm/Config.unix
index 8f2f140247..339c3c3ffb 100644
--- a/vm/Config.unix
+++ b/vm/Config.unix
@@ -5,7 +5,7 @@ endif
 EXE_SUFFIX =
 DLL_PREFIX = lib
 DLL_EXTENSION = .a
-# DLL_EXTENSION = .so
+SHARED_DLL_EXTENSION = .so
 SHARED_FLAG = -shared
 
 PLAF_DLL_OBJS = vm/os-unix.o
diff --git a/vm/Config.windows b/vm/Config.windows
index 75452a9bb4..cdb72f4e24 100644
--- a/vm/Config.windows
+++ b/vm/Config.windows
@@ -5,5 +5,6 @@ SHARED_FLAG = -shared
 EXE_EXTENSION=.exe
 CONSOLE_EXTENSION=.com
 DLL_EXTENSION=.dll
+SHARED_DLL_EXTENSION=.dll
 LINKER = $(CC) -shared -mno-cygwin -o 
 LINK_WITH_ENGINE = -l$(DLL_PREFIX)factor$(DLL_SUFFIX)