diff --git a/tools/bzl/asciidoc.bzl b/tools/bzl/asciidoc.bzl
index ea082466ba..baa192db9b 100644
--- a/tools/bzl/asciidoc.bzl
+++ b/tools/bzl/asciidoc.bzl
@@ -137,9 +137,9 @@ _asciidoc_attrs = {
 }
 
 _asciidoc = rule(
-    attrs = _asciidoc_attrs + {
+    attrs = dict(_asciidoc_attrs.items() + {
         "outs": attr.output_list(mandatory = True),
-    },
+    }.items()),
     implementation = _asciidoc_impl,
 )
 
diff --git a/tools/bzl/js.bzl b/tools/bzl/js.bzl
index 39d6acfbbf..783c79c0c7 100644
--- a/tools/bzl/js.bzl
+++ b/tools/bzl/js.bzl
@@ -184,10 +184,10 @@ def _js_component(ctx):
 
 js_component = rule(
     _js_component,
-    attrs = _common_attrs + {
+    attrs = dict(_common_attrs.items() + {
         "srcs": attr.label_list(allow_files = [".js"]),
         "license": attr.label(allow_single_file = True),
-    },
+    }.items()),
     outputs = {
         "zip": "%{name}.zip",
     },
@@ -195,14 +195,14 @@ js_component = rule(
 
 _bower_component = rule(
     _bower_component_impl,
-    attrs = _common_attrs + {
+    attrs = dict(_common_attrs.items() + {
         "zipfile": attr.label(allow_single_file = [".zip"]),
         "license": attr.label(allow_single_file = True),
         "version_json": attr.label(allow_files = [".json"]),
 
         # If set, define by hand, and don't regenerate this entry in bower2bazel.
         "seed": attr.bool(default = False),
-    },
+    }.items()),
 )
 
 # TODO(hanwen): make license mandatory.