diff --git a/configure.ac b/configure.ac
index 54d92c238..84c66624b 100644
--- a/configure.ac
+++ b/configure.ac
@@ -178,12 +178,13 @@ AC_ARG_ENABLE([debug],
     [enable_debug=no])
 
 if test "x$enable_debug" = xyes; then
+    CPPFLAGS="$CPPFLAGS -DDEBUG -DDEBUG_LOCKORDER"
     if test "x$GCC" = xyes; then
-        CFLAGS="-g3 -O0 -DDEBUG"
+        CFLAGS="$CFLAGS -g3 -O0"
     fi
 
     if test "x$GXX" = xyes; then
-        CXXFLAGS="-g3 -O0 -DDEBUG"
+        CXXFLAGS="$CXXFLAGS -g3 -O0"
     fi
 fi