--- a/configure.in
+++ b/configure.in
@@ -773,17 +773,17 @@ AC_MSG_CHECKING([for full perl installat
 if test "$_perl_res" != 0; then
     AC_MSG_RESULT([no])
     AC_MSG_ERROR([Cannot find Config.pm or \$Config{archlib}.  A full perl installation is required.])
 else
     AC_MSG_RESULT([yes])
 fi
 
 if test -z "$COMPILE_ENVIRONMENT"; then
-    NSINSTALL_BIN='$(PYTHON) $(topsrcdir)/config/nsinstall.py'
+    NSINSTALL_BIN='$(PYTHON) $(MOZILLA_DIR)/config/nsinstall.py'
 fi
 AC_SUBST(NSINSTALL_BIN)
 
 MOZ_PATH_PROG(DOXYGEN, doxygen, :)
 MOZ_PATH_PROG(AUTOCONF, autoconf, :)
 MOZ_PATH_PROGS(UNZIP, unzip)
 if test -z "$UNZIP" -o "$UNZIP" = ":"; then
     AC_MSG_ERROR([unzip not found in \$PATH])