diff --git a/sapi/phpdbg/config.m4 b/sapi/phpdbg/config.m4
index ca8758fa6737b..a2d37633f7472 100644
--- a/sapi/phpdbg/config.m4
+++ b/sapi/phpdbg/config.m4
@@ -27,8 +27,6 @@ if test "$PHP_PHPDBG" != "no"; then
   AS_VAR_IF([PHP_PHPDBG_DEBUG], [no],,
     [AS_VAR_APPEND([PHP_PHPDBG_CFLAGS], [" -DPHPDBG_DEBUG=1"])])
 
-  PHP_PHPDBG_FILES="phpdbg.c phpdbg_parser.c phpdbg_lexer.c phpdbg_prompt.c phpdbg_help.c phpdbg_break.c phpdbg_print.c phpdbg_bp.c phpdbg_list.c phpdbg_utils.c phpdbg_info.c phpdbg_cmd.c phpdbg_set.c phpdbg_frame.c phpdbg_watch.c phpdbg_btree.c phpdbg_sigsafe.c phpdbg_io.c phpdbg_out.c"
-
   AC_MSG_CHECKING([for phpdbg and readline integration])
   if test "$PHP_PHPDBG_READLINE" = "yes"; then
     if test "$PHP_READLINE" != "no" || test "$PHP_LIBEDIT" != "no"; then
@@ -69,7 +67,27 @@ if test "$PHP_PHPDBG" != "no"; then
     [$abs_builddir/sapi/phpdbg])
   PHP_SELECT_SAPI([phpdbg],
     [program],
-    [$PHP_PHPDBG_FILES],
+    m4_normalize([
+      phpdbg_bp.c
+      phpdbg_break.c
+      phpdbg_btree.c
+      phpdbg_cmd.c
+      phpdbg_frame.c
+      phpdbg_help.c
+      phpdbg_info.c
+      phpdbg_io.c
+      phpdbg_lexer.c
+      phpdbg_list.c
+      phpdbg_out.c
+      phpdbg_parser.c
+      phpdbg_print.c
+      phpdbg_prompt.c
+      phpdbg_set.c
+      phpdbg_sigsafe.c
+      phpdbg_utils.c
+      phpdbg_watch.c
+      phpdbg.c
+    ]),
     [$PHP_PHPDBG_CFLAGS])
 
   BUILD_BINARY="sapi/phpdbg/phpdbg"