diff --git a/src/rez/config.py b/src/rez/config.py
index 964200ff59..6e63720aa4 100644
--- a/src/rez/config.py
+++ b/src/rez/config.py
@@ -3,6 +3,7 @@
 from rez.utils.data_utils import AttrDictWrapper, RO_AttrDictWrapper, \
     convert_dicts, cached_property, cached_class_property, LazyAttributeMeta, \
     deep_update, ModifyList
+from rez.utils.datatypes import HashableDict
 from rez.utils.formatting import expandvars, expanduser
 from rez.utils.logging_ import get_debug_printer
 from rez.utils.scope import scoped_format
@@ -819,7 +820,7 @@ def _replace_config(other):
 
 
 @lru_cache()
-def _load_config_py(filepath):
+def _load_config_py(filepath, fallback_platform_map):
     from rez.utils.data_utils import Conditional, PlatformDependent, \
         InConfigArchDependent, InConfigOsDependent
     reserved = dict(
@@ -828,13 +829,14 @@ def _load_config_py(filepath):
         # and later excluded from the `Config` class
         __name__=os.path.splitext(os.path.basename(filepath))[0],
         __file__=filepath,
+        __fallback_platform_map=fallback_platform_map,
 
         rez_version=__version__,
         ModifyList=ModifyList,
         Conditional=Conditional,
         PlatformDependent=PlatformDependent,
         ArchDependent=InConfigArchDependent,
-        OsDependent=InConfigOsDependent
+        OsDependent=InConfigOsDependent,
     )
 
     g = reserved.copy()
@@ -851,14 +853,15 @@ def _load_config_py(filepath):
     for k, v in g.items():
         if k != '__builtins__' \
                 and not ismodule(v) \
-                and k not in reserved:
+                and k not in reserved \
+                and k != "__fallback_platform_map":
             result[k] = v
 
     return result
 
 
 @lru_cache()
-def _load_config_yaml(filepath):
+def _load_config_yaml(filepath, _):
     with open(filepath) as f:
         content = f.read()
     try:
@@ -890,7 +893,11 @@ def _load_config_from_filepaths(filepaths):
             if not os.path.isfile(filepath_with_ext):
                 continue
 
-            data_ = loader(filepath_with_ext)
+            previous_platform_map = data.get("platform_map", None)
+            if previous_platform_map is not None:
+                previous_platform_map = HashableDict(previous_platform_map)
+
+            data_ = loader(filepath_with_ext, previous_platform_map)
             deep_update(data, data_)
             sourced_filepaths.append(filepath_with_ext)
             break
diff --git a/src/rez/tests/data/config/test_conditional_dependee.py b/src/rez/tests/data/config/test_conditional_dependee.py
new file mode 100644
index 0000000000..71fcc3860c
--- /dev/null
+++ b/src/rez/tests/data/config/test_conditional_dependee.py
@@ -0,0 +1,4 @@
+
+dot_image_format = ArchDependent({
+    "IMPOSSIBLE_ARCH": "hello",
+})
diff --git a/src/rez/tests/test_config.py b/src/rez/tests/test_config.py
index 011139d8ce..bde32d2f1c 100644
--- a/src/rez/tests/test_config.py
+++ b/src/rez/tests/test_config.py
@@ -139,6 +139,19 @@ def test_conditional_in_file(self):
         self.assertEqual(c.prune_failed_graph, True)
         self.assertEqual(c.warn_all, True)
 
+    def test_conidition_nested(self):
+        conf = os.path.join(self.config_path, "test_conditional.py")
+        conf_dependee = os.path.join(self.config_path, "test_conditional_dependee.py")
+        c = Config([conf, conf_dependee])
+        self.assertEqual(c.dot_image_format, "hello")
+
+    def test_conidition_nested_inbeween(self):
+        conf = os.path.join(self.config_path, "test_conditional.py")
+        conf_middle = os.path.join(self.config_path, "test2.py")
+        conf_dependee = os.path.join(self.config_path, "test_conditional_dependee.py")
+        c = Config([conf, conf_middle, conf_dependee])
+        self.assertEqual(c.dot_image_format, "hello")
+
     def test_1(self):
         """Test just the root config file."""
 
diff --git a/src/rez/utils/data_utils.py b/src/rez/utils/data_utils.py
index 395ccf3534..f1ce0f8805 100644
--- a/src/rez/utils/data_utils.py
+++ b/src/rez/utils/data_utils.py
@@ -683,7 +683,10 @@ def __new__(cls, base, frame, options, default=ConditionalConfigurationError):
         # a global config.
         platform_map = frame.f_locals.get(
             "platform_map",
-            None
+            frame.f_locals.get(
+                "__fallback_platform_map",
+                None
+            )
         )
 
         return base(options, default, platform_map=platform_map)
diff --git a/src/rez/utils/datatypes.py b/src/rez/utils/datatypes.py
new file mode 100644
index 0000000000..09ba538fb7
--- /dev/null
+++ b/src/rez/utils/datatypes.py
@@ -0,0 +1,26 @@
+
+
+class HashableDict(dict):
+    """
+    Hashable dict (immutable by definition)
+    """
+
+    def __init__(self, other=None):
+        super(HashableDict, self).__init__()
+        if other:
+            for k, v in other.items():
+                if isinstance(v, dict):
+                    self[k] = HashableDict(v)
+                else:
+                    self[k] = v
+
+    def __key(self):
+        return tuple((k,self[k]) for k in sorted(self))
+
+    def __hash__(self):
+        return hash(self.__key())
+
+    def __eq__(self, other):
+        return self.__key() == other.__key()
+
+