diff --git a/js/src/old-configure.in b/js/src/old-configure.in
index e8573a4c308e..c65f294717f3 100644
--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -2030,11 +2030,11 @@ 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)
diff --git a/old-configure.in b/old-configure.in
index 43e5fc9307be..1aee9df832b4 100644
--- a/old-configure.in
+++ b/old-configure.in
@@ -4825,11 +4825,11 @@ 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)