--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -2025,21 +2025,21 @@ AC_SUBST_LIST(OS_CXXFLAGS)
 AC_SUBST_LIST(OS_CPPFLAGS)
 AC_SUBST_LIST(OS_COMPILE_CFLAGS)
 AC_SUBST_LIST(OS_COMPILE_CXXFLAGS)
 AC_SUBST(OS_LDFLAGS)
 AC_SUBST(OS_LIBS)
 
 AC_SUBST(HOST_CC)
 AC_SUBST(HOST_CXX)
-AC_SUBST(HOST_CFLAGS)
-AC_SUBST(HOST_CPPFLAGS)
-AC_SUBST(HOST_CXXFLAGS)
+AC_SUBST_LIST(HOST_CFLAGS)
+AC_SUBST_LIST(HOST_CPPFLAGS)
+AC_SUBST_LIST(HOST_CXXFLAGS)
 AC_SUBST(HOST_LDFLAGS)
-AC_SUBST(HOST_OPTIMIZE_FLAGS)
+AC_SUBST_LIST(HOST_OPTIMIZE_FLAGS)
 AC_SUBST(HOST_AR)
 AC_SUBST(HOST_AR_FLAGS)
 AC_SUBST(HOST_RANLIB)
 AC_SUBST(HOST_BIN_SUFFIX)
 
 AC_SUBST(TARGET_XPCOM_ABI)
 
 AC_SUBST(WRAP_LDFLAGS)

--- a/old-configure.in
+++ b/old-configure.in
@@ -4821,21 +4821,21 @@ AC_SUBST_LIST(OS_CXXFLAGS)
 AC_SUBST_LIST(OS_CPPFLAGS)
 AC_SUBST_LIST(OS_COMPILE_CFLAGS)
 AC_SUBST_LIST(OS_COMPILE_CXXFLAGS)
 AC_SUBST(OS_LDFLAGS)
 AC_SUBST(OS_LIBS)
 
 AC_SUBST(HOST_CC)
 AC_SUBST(HOST_CXX)
-AC_SUBST(HOST_CFLAGS)
-AC_SUBST(HOST_CPPFLAGS)
-AC_SUBST(HOST_CXXFLAGS)
+AC_SUBST_LIST(HOST_CFLAGS)
+AC_SUBST_LIST(HOST_CPPFLAGS)
+AC_SUBST_LIST(HOST_CXXFLAGS)
 AC_SUBST(HOST_LDFLAGS)
-AC_SUBST(HOST_OPTIMIZE_FLAGS)
+AC_SUBST_LIST(HOST_OPTIMIZE_FLAGS)
 AC_SUBST(HOST_AR)
 AC_SUBST(HOST_AR_FLAGS)
 AC_SUBST(HOST_RANLIB)
 AC_SUBST(HOST_BIN_SUFFIX)
 
 AC_SUBST(TARGET_XPCOM_ABI)
 AC_SUBST(HAVE_TOOLCHAIN_SUPPORT_MSSSE3)
 AC_SUBST(HAVE_TOOLCHAIN_SUPPORT_MSSE4_1)