diff --git a/README.md b/README.md
index 52c741f3..804357fe 100644
--- a/README.md
+++ b/README.md
@@ -29,8 +29,9 @@ capabilities, so these can continue to be used by containers.
 
 To run weave on a host, you need to install...
 
-1. docker. We've tested with versions 0.9.1 through 1.2.0, but other
-   versions should work too.
+1. Linux and Docker. We've tested with Docker versions 0.9.1 through
+   1.2.0, but other versions should work too. Linux kernels after 3.5
+   are known to work; the newer the better.
 2. weave. Install this with
 
         sudo wget -O /usr/local/bin/weave \
diff --git a/weave b/weave
index 270e3778..02c501f1 100755
--- a/weave
+++ b/weave
@@ -338,6 +338,19 @@ container_weave_addrs() {
     ip netns exec $NETNS ip addr show dev $CONTAINER_IFNAME
 }
 
+uname_sys=`uname -s`
+uname_rel_major=`uname -r | cut -d. -f1`
+uname_rel_minor=`uname -r | cut -d. -f2`
+
+[ ! $uname_sys = 'Linux' ] && {
+  echo "ERROR: Operating systems other than Linux are not supported (you have $uname_sys)" >&2
+  exit 1
+}
+
+(([ $uname_rel_major -eq 3 ] && [ $uname_rel_minor -ge 5 ]) || [ $uname_rel_major -gt 3 ]) || {
+  echo "WARNING: Linux kernel version 3.5 or newer is required (you have `uname -sr`)" >&2
+}
+
 case "$COMMAND" in
     launch)
         check_not_running $CONTAINER_NAME $IMAGE