diff --git a/.travis.yml b/.travis.yml
index 5422518..194b715 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -3,6 +3,9 @@ php:
   - 5.5
   - 5.4
   - 5.3
+env:
+  - V8VER=3.22.22
+  - V8VER=3.21.12
 before_install: make -f Makefile.travis before_install
 install: make -f Makefile.travis install
 script: make -f Makefile.travis test
diff --git a/Makefile.travis b/Makefile.travis
index 190f17c..ef18367 100644
--- a/Makefile.travis
+++ b/Makefile.travis
@@ -1,6 +1,6 @@
 # Configure and build scripts for travis CI system
-V8VER=3.22.10
-CPPVER=4.6
+V8VER ?= 3.22.10
+CPPVER ?= 4.6
 
 export CXX=g++-$(CPPVER)
 export LINK=g++-$(CPPVER)