diff --git a/core/product_config.rbc b/core/product_config.rbc
index da8209b0fc..97c1d00471 100644
--- a/core/product_config.rbc
+++ b/core/product_config.rbc
@@ -462,6 +462,9 @@ def _addsuffix(suffix, string_or_list):
 
 def __words(string_or_list):
     if type(string_or_list) == "list":
+        for x in string_or_list:
+            if type(x) != "string":
+                return string_or_list
         string_or_list = " ".join(string_or_list)
     return _mkstrip(string_or_list).split()
 
diff --git a/tests/run.rbc b/tests/run.rbc
index 1b51719e6f..33583eb3cd 100644
--- a/tests/run.rbc
+++ b/tests/run.rbc
@@ -46,6 +46,11 @@ assert_eq("", rblf.mkstrip(" \n \t    "))
 assert_eq("a b c", rblf.mkstrip("  a b   \n  c \t"))
 assert_eq("1", rblf.mkstrip("1 "))
 
+assert_eq(["a", "b"], rblf.words("a b"))
+assert_eq(["a", "b", "c"], rblf.words(["a b", "c"]))
+# 1-tuple like we use in product variables
+assert_eq(["a b", ("c",)], rblf.words(["a b", ("c",)]))
+
 assert_eq("b1 b2", rblf.mksubst("a", "b", "a1 a2"))
 assert_eq(["b1", "x2"], rblf.mksubst("a", "b", ["a1", "x2"]))