diff --git a/core/product_config.rbc b/core/product_config.rbc
index 7a5e50110b..b3156c6f39 100644
--- a/core/product_config.rbc
+++ b/core/product_config.rbc
@@ -830,6 +830,37 @@ def _product_copy_files_by_pattern(src, dest, s):
     return [ __mkpatsubst_word(parsed_percent, parsed_src, x) + ":" + __mkpatsubst_word(parsed_percent, parsed_dest, x) for x in words]
 
 
+__zero_values = {
+    "string": "",
+    "list": [],
+    "int": 0,
+    "float": 0,
+    "bool": False,
+    "dict": {},
+    "NoneType": None,
+    "tuple": (),
+}
+def __zero_value(x):
+    t = type(x)
+    if t in __zero_values:
+        return __zero_values[t]
+    else:
+        fail("Unknown type: "+t)
+
+
+def _clear_var_list(g, h, var_list):
+    cfg = __h_cfg(h)
+    for v in __words(var_list):
+        # Set these variables to their zero values rather than None
+        # or removing them from the dictionary because if they were
+        # removed entirely, ?= would set their value, when it would not
+        # after a make-based clear_var_list call.
+        if v in g:
+            g[v] = __zero_value(g[v])
+        if v in cfg:
+            cfg[v] = __zero_value(cfg[v])
+
+
 def __get_options():
     """Returns struct containing runtime global settings."""
     settings = dict(
@@ -873,6 +904,7 @@ rblf = struct(
     addsuffix = _addsuffix,
     board_platform_in = _board_platform_in,
     board_platform_is = _board_platform_is,
+    clear_var_list = _clear_var_list,
     copy_files = _copy_files,
     copy_if_exists = _copy_if_exists,
     cfg = __h_cfg,
diff --git a/tests/run.rbc b/tests/run.rbc
index c6dfeba405..06f56d324d 100644
--- a/tests/run.rbc
+++ b/tests/run.rbc
@@ -162,6 +162,16 @@ assert_eq(
 assert_eq({"A_LIST_VARIABLE": ["foo", "bar"]}, board_globals)
 assert_eq({"A_LIST_VARIABLE": ["foo"]}, board_globals_base)
 
+g = {"FOO": "a", "BAR": "c", "BAZ": "e"}
+cfg = {"FOO": "b", "BAR": "d", "BAZ": "f"}
+rblf.clear_var_list(g, struct(cfg=cfg), "FOO BAR")
+assert_eq("", g["FOO"])
+assert_eq("", cfg["FOO"])
+assert_eq("", g["BAR"])
+assert_eq("", cfg["BAR"])
+assert_eq("e", g["BAZ"])
+assert_eq("f", cfg["BAZ"])
+
 test_single_value_inheritance()
 test_artifact_path_requirements()
 test_prefixed_sort_order()