diff --git a/weave b/weave
index 73254d8c..57bc1aab 100755
--- a/weave
+++ b/weave
@@ -1095,9 +1095,14 @@ launch_router() {
     if [ -z "$IPRANGE_SPECIFIED" ] ; then
         IPRANGE="10.32.0.0/12"
         if command_exists netcheck && ! netcheck --ignore-iface=$BRIDGE $IPRANGE ; then
-            echo "Default --ipalloc-range $IPRANGE overlaps with existing route on host." >&2
-            echo "Please pick another range and set it on all hosts." >&2
+                echo "ERROR: Default --ipalloc-range $IPRANGE overlaps with existing route on host." >&2
+                echo "You must pick another range and set it on all hosts." >&2
             exit 1
+            fi
+        else
+            if command_exists netcheck && ! netcheck --ignore-iface=$BRIDGE $IPRANGE ; then
+                echo "WARNING: Specified --ipalloc-range $IPRANGE overlaps with existing route on host." >&2
+                echo "Unless this is deliberate, you must pick another range and set it on all hosts." >&2
         fi
     fi
     # Set WEAVE_DOCKER_ARGS in the environment in order to supply