diff --git a/Makefile b/Makefile
index a3cdac5f..7fbb7d1f 100644
--- a/Makefile
+++ b/Makefile
@@ -60,6 +60,8 @@ setup:
 test:
 	$(ISTANBUL) cover node_modules/.bin/_mocha -- --recursive --timeout 10000
 	$(ISTANBUL) check-coverage --branches 100
-ifneq ($(shell node --version | sed 's/[.][^.]*$$//'),v0.10)
+ifeq ($(shell node --version | cut -d . -f 1),v6)
 	$(DOCTEST) -- index.js
+else
+	@echo '[WARN] Doctests are only run in Node v6.x.x (current version is $(shell node --version))' >&2
 endif
diff --git a/circle.yml b/circle.yml
index c176f229..ab09a423 100644
--- a/circle.yml
+++ b/circle.yml
@@ -1,7 +1,8 @@
 dependencies:
   override:
+    - printf '%s\n' color=false progress=false >.npmrc
     - rm -rf node_modules
-    - case $CIRCLE_NODE_INDEX in 0) make setup ;; 1) nvm exec 0.12.7 make setup ;; 2) nvm exec 4 make setup ;; 3) nvm exec 5 make setup ;; esac:
+    - case $CIRCLE_NODE_INDEX in 0) make setup ;; 1) nvm exec 0.12.7 make setup ;; 2) nvm exec 4 make setup ;; 3) nvm install 6 && nvm exec 6 make setup ;; esac:
         parallel: true
 
 machine:
@@ -11,5 +12,5 @@ machine:
 test:
   override:
     - make lint
-    - case $CIRCLE_NODE_INDEX in 0) make test ;; 1) nvm exec 0.12.7 make test ;; 2) nvm exec 4 make test ;; 3) nvm exec 5 make test ;; esac:
+    - case $CIRCLE_NODE_INDEX in 0) make test ;; 1) nvm exec 0.12.7 make test ;; 2) nvm exec 4 make test ;; 3) nvm exec 6 make test ;; esac:
         parallel: true
diff --git a/index.js b/index.js
index 275d724d..a2ccadc8 100644
--- a/index.js
+++ b/index.js
@@ -1983,10 +1983,10 @@
   //. Right(['foo', 'bar', 'baz'])
   //.
   //. > S.encaseEither(S.I, JSON.parse, '[')
-  //. Left(new SyntaxError('Unexpected end of input'))
+  //. Left(new SyntaxError('Unexpected end of JSON input'))
   //.
   //. > S.encaseEither(S.prop('message'), JSON.parse, '[')
-  //. Left('Unexpected end of input')
+  //. Left('Unexpected end of JSON input')
   //. ```
   S.encaseEither =
   def('encaseEither',