diff --git a/Makefile.in b/Makefile.in
index 823a393..5bdae04 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -97,9 +97,6 @@ THREAD_VFS_ROOT		= libthread.vfs
 THREAD_VFS_PATH		= ${THREAD_VFS_ROOT}/thread_library
 
 ZIPFS_BUILD		= @ZIPFS_BUILD@
-NATIVE_ZIP		= @ZIP_PROG@
-ZIP_PROG_OPTIONS	= @ZIP_PROG_OPTIONS@
-ZIP_PROG_VFSSEARCH	= @ZIP_PROG_VFSSEARCH@
 SHARED_BUILD		= @SHARED_BUILD@
 INSTALL_LIBRARIES	= @INSTALL_LIBRARIES@
 INSTALL_MSGS		= @INSTALL_MSGS@
diff --git a/pkgIndex.tcl.in b/pkgIndex.tcl.in
index 5ef1382..aaf64fd 100755
--- a/pkgIndex.tcl.in
+++ b/pkgIndex.tcl.in
@@ -39,7 +39,8 @@ package ifneeded ttrace @PACKAGE_VERSION@ [list ::apply {{dir} {
 	source [file join $dir .. lib ttrace.tcl]
     } elseif {[file readable [file join $dir ttrace.tcl]]} {
 	source [file join $dir ttrace.tcl]
-    } elseif {![catch {zipfs mount [file join $dir @PKG_LIB_FILE@] //zipfs:/lib/thread}]} {
+    } elseif {[file exists //zipfs:/lib/thread/ttrace.tcl] ||
+              ![catch {zipfs mount [file join $dir @PKG_LIB_FILE@] //zipfs:/lib/thread}]} {
 	source //zipfs:/lib/thread/ttrace.tcl
     }
     if {[namespace which ::ttrace::update] ne ""} {