diff --git a/configure b/configure
index dd000b28fe3..a966217eba9 100755
--- a/configure
+++ b/configure
@@ -9768,7 +9768,7 @@ fi
 { $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_crosscflags__Werror_unknown_warning_option" >&5
 $as_echo "$ac_cv_crosscflags__Werror_unknown_warning_option" >&6; }
 if test "x$ac_cv_crosscflags__Werror_unknown_warning_option" = xyes; then :
-  EXTRACROSSCFLAGS="$EXTRACROSSCFLAGS -Werror=unknown-warning-option"
+  CFLAGS="$CFLAGS -Werror=unknown-warning-option"
 fi
         { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether the cross-compiler supports -Wdeclaration-after-statement" >&5
 $as_echo_n "checking whether the cross-compiler supports -Wdeclaration-after-statement... " >&6; }
diff --git a/configure.ac b/configure.ac
index ad4f0e05a40..d8ab7823c1f 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1024,7 +1024,7 @@ then
                           [AC_MSG_RESULT([no])])
         WINE_TRY_CROSSCFLAGS([-fno-strict-aliasing])
         dnl clang needs to be told to fail on unknown options
-        WINE_TRY_CROSSCFLAGS([-Werror=unknown-warning-option])
+        WINE_TRY_CROSSCFLAGS([-Werror=unknown-warning-option],[CFLAGS="$CFLAGS -Werror=unknown-warning-option"])
         WINE_TRY_CROSSCFLAGS([-Wdeclaration-after-statement])
         WINE_TRY_CROSSCFLAGS([-Wempty-body])
         WINE_TRY_CROSSCFLAGS([-Wignored-qualifiers])