diff --git a/configure.ac b/configure.ac
index 861432a5b23..5d25dc864c3 100644
--- a/configure.ac
+++ b/configure.ac
@@ -3717,6 +3717,7 @@ AC_SUBST(CFLAGS)
 AC_SUBST(CXXFLAGS)
 AC_SUBST(GDC)
 AC_SUBST(GDCFLAGS)
+GDCFLAGS=${GDCFLAGS-${CFLAGS}}
 AC_SUBST(PKG_CONFIG_PATH)
 
 GCC_PLUGIN_OPTION(PLUGIN_OPTION)