diff --git a/.travis.yml b/.travis.yml
index 359a7039ff..4cd4f468f5 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -65,9 +65,12 @@ matrix:
             test \
             //... $REMOTE_FLAGS
         
-        # Check that BUILD files are formatted  correctly.
+        # Check that BUILD files are formatted correctly.
         - ./check_gazelle.sh
 
+        # Check that target visibility is correct..
+        - ./check_visibility.sh
+
         # Shutdown must be last.
         - bazel shutdown 
           
diff --git a/beacon-chain/network/BUILD.bazel b/beacon-chain/network/BUILD.bazel
index db27f9401b..aad899e82a 100644
--- a/beacon-chain/network/BUILD.bazel
+++ b/beacon-chain/network/BUILD.bazel
@@ -4,7 +4,7 @@ go_library(
     name = "go_default_library",
     srcs = ["service.go"],
     importpath = "github.com/prysmaticlabs/prysm/beacon-chain/network",
-    visibility = ["//visibility:public"],
+    visibility = ["//beacon-chain:__subpackages__"],
     deps = [
         "//beacon-chain/types:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
diff --git a/beacon-chain/sync/BUILD.bazel b/beacon-chain/sync/BUILD.bazel
index 08e177dcdf..e0d37de9b1 100644
--- a/beacon-chain/sync/BUILD.bazel
+++ b/beacon-chain/sync/BUILD.bazel
@@ -4,7 +4,7 @@ go_library(
     name = "go_default_library",
     srcs = ["service.go"],
     importpath = "github.com/prysmaticlabs/prysm/beacon-chain/sync",
-    visibility = ["//visibility:public"],
+    visibility = ["//beacon-chain:__subpackages__"],
     deps = [
         "//beacon-chain/types:go_default_library",
         "@com_github_sirupsen_logrus//:go_default_library",
diff --git a/check_visibility.sh b/check_visibility.sh
new file mode 100755
index 0000000000..2bfcb64458
--- /dev/null
+++ b/check_visibility.sh
@@ -0,0 +1,29 @@
+#!/bin/bash
+
+# Continous Integration script to check that BUILD.bazel files have the correct
+# visibility.
+
+# Protected packages are:
+#   //beacon-chain/...
+#   //client/...
+
+# Duplicate redirect 5 to stdout so that it can be captured, but still printed
+# nicely.
+exec 5>&1
+
+# Run gazelle while piping a copy of the output to stdout via 5.
+changes=$(
+bazel query 'visible(//... except (//beacon-chain/... union //client/...), (//beacon-chain/... union //client/...))' | tee >(cat - >&5)
+)
+
+# If the captured stdout is not empty then targets are exposed!
+if [ -z "$changes" ]
+then
+  echo "OK: Visibility is good."
+  exit 0
+else
+  echo "FAIL: The above targets belong to protected packages and the targets \
+are visible outside of their package!"
+  echo "Please reduce the target visibility."
+  exit 1
+fi