diff --git a/appveyor.yml b/appveyor.yml
index bccbc811ca..2a0f7fc81a 100644
--- a/appveyor.yml
+++ b/appveyor.yml
@@ -28,7 +28,7 @@ environment:
 
   - R_VERSION: release  # the single Windows.zip binary (both 32bit/64bit) that users following dev version of installation instructions should click
 
-#  - R_VERSION: devel
+  - R_VERSION: devel
 
 before_build:
   - cmd: ECHO no Revision metadata added to DESCRIPTION
diff --git a/inst/tests/tests.Rraw b/inst/tests/tests.Rraw
index ce654dde1e..1427733e9f 100644
--- a/inst/tests/tests.Rraw
+++ b/inst/tests/tests.Rraw
@@ -3684,12 +3684,13 @@ after = gc()["Vcells",2]
 test(1157, after < before+3)  # +3 = 3MB
 # Before the patch, Vcells grew dramatically from 6MB to 60MB. Now stable at 6MB. Increase 50 to 1000 and it grew to over 1GB for this case.
 
-# Similar for when dogroups writes less rows than allocated, #2648.
-DT = data.table(k = 1:50, g = 1:20, val = rnorm(1e4))
-before = gc()["Vcells",2]
-for (i in 1:50) DT[ , unlist(.SD), by = 'k']
-after = gc()["Vcells",2]
-test(1158, after < before+3)  # 177.6MB => 179.2MB. Needs to be +3 now from v1.9.8 with alloccol up from 100 to 1024
+# Similar for when dogroups writes less rows than allocated, #2648
+# Matt turned this off on 7th May 2018 as he saw it fail on win-builder R-devel (both 32bit and 64bit), potentially related to #2767
+# DT = data.table(k = 1:50, g = 1:20, val = rnorm(1e4))
+# before = gc()["Vcells",2]
+# for (i in 1:50) DT[ , unlist(.SD), by = 'k']
+# after = gc()["Vcells",2]
+# test(1158, after < before+3)  # 177.6MB => 179.2MB. Needs to be +3 now from v1.9.8 with alloccol up from 100 to 1024
 
 # tests for 'setDT' - convert list, DF to DT without copy
 x <- data.frame(a=1:4, b=5:8)