diff --git a/core/product_config.rbc b/core/product_config.rbc
index c0bf281fb8..c53ddbf4ed 100644
--- a/core/product_config.rbc
+++ b/core/product_config.rbc
@@ -228,13 +228,15 @@ def _dictionary_difference(a, b):
     return result
 
 def _board_configuration(board_config_init, input_variables_init):
+    globals_base = {}
+    h_base = __h_new()
     globals = {}
     h = __h_new()
+
+    input_variables_init(globals_base, h_base)
     input_variables_init(globals, h)
-    cfg_base = dict(**h[0])
-    globals_base = dict(**globals)
     board_config_init(globals, h)
-    return (globals, _dictionary_difference(h[0], cfg_base), globals_base)
+    return (globals, _dictionary_difference(h[0], h_base[0]), globals_base)
 
 
 def _substitute_inherited(configs, pcm_name, cfg):
diff --git a/tests/board.rbc b/tests/board.rbc
new file mode 100644
index 0000000000..8696e4068d
--- /dev/null
+++ b/tests/board.rbc
@@ -0,0 +1,19 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["A_LIST_VARIABLE"] += ["bar"]
diff --git a/tests/board_input_vars.rbc b/tests/board_input_vars.rbc
new file mode 100644
index 0000000000..69d9cd62c7
--- /dev/null
+++ b/tests/board_input_vars.rbc
@@ -0,0 +1,19 @@
+# Copyright 2021 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#      https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+load("//build/make/core:product_config.rbc", "rblf")
+
+def init(g, handle):
+  cfg = rblf.cfg(handle)
+  g["A_LIST_VARIABLE"] = ["foo"]
diff --git a/tests/device.rbc b/tests/product.rbc
similarity index 100%
rename from tests/device.rbc
rename to tests/product.rbc
diff --git a/tests/run.rbc b/tests/run.rbc
index 31436c57d8..2afee087fe 100644
--- a/tests/run.rbc
+++ b/tests/run.rbc
@@ -13,8 +13,8 @@
 # limitations under the License.
 
 
-# Run test configuration and verify its result.
-# The main configuration file is device.rbc.
+# Run test product configuration and verify its result.
+# The main configuration file is product.rbc.
 # It inherits part1.rbc and also includes include1.rbc
 # TODO(asmundak): more tests are needed to verify that:
 #  * multi-level inheritance works as expected
@@ -22,7 +22,9 @@
 
 load("//build/make/core:product_config.rbc", "rblf")
 load(":version_defaults.rbc", "version_defaults")
-load(":device.rbc", "init")
+load(":product.rbc", "init")
+load(":board.rbc", board_init = "init")
+load(":board_input_vars.rbc", board_input_vars_init = "init")
 
 def assert_eq(expected, actual):
     if expected != actual:
@@ -110,3 +112,7 @@ assert_eq(
     },
     { k:v for k,v in sorted(goals.items()) }
 )
+
+(board_globals, board_config, board_globals_base) = rblf.board_configuration(board_init, board_input_vars_init)
+assert_eq({"A_LIST_VARIABLE": ["foo", "bar"]}, board_globals)
+assert_eq({"A_LIST_VARIABLE": ["foo"]}, board_globals_base)