diff --git a/tools/targets.py b/tools/targets.py
index 73a3c0a840b..3d4a3b380c8 100644
--- a/tools/targets.py
+++ b/tools/targets.py
@@ -48,9 +48,9 @@ class HookError(Exception):
 caches = {}
 def cached(func):
     def wrapper(*args, **kwargs):
-        if not caches.has_key(func):
-            caches[func] = func(*args, **kwargs)
-        return caches[func]
+        if not caches.has_key((func.__name__, args)):
+            caches[(func.__name__, args)] = func(*args, **kwargs)
+        return caches[(func.__name__, args)]
     return wrapper
 
 class Target:
@@ -58,17 +58,21 @@ class Target:
     # need to be computed differently than regular attributes
     __cumulative_attributes = ['extra_labels', 'macros', 'device_has', 'features']
 
-    # {target_name: target_instance} map for all the targets in the system
-    __target_map = {}
-
-    # List of targets that were added dynamically using "add_py_targets" (see below)
-    __py_targets = set()
+    # Location of the 'targets.json' file
+    __targets_json_location = os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', 'hal', 'targets.json')
 
     # Load the description of JSON target data
     @staticmethod
     @cached
     def get_json_target_data():
-        return json_file_to_dict(os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', 'hal', 'targets.json'))
+        return json_file_to_dict(Target.__targets_json_location)
+
+    # Set the location of the targets.json file
+    @staticmethod
+    def set_targets_json_location(location):
+        Target.__targets_json_location = location
+        # Invalidate caches, since the location of the JSON file changed
+        caches.clear()
 
     # Get the members of this module using Python's "inspect" module
     @staticmethod
@@ -168,42 +172,26 @@ def __getattr__(self, attrname):
         return v
 
     # Add one or more new target(s) represented as a Python dictionary in 'new_targets'
-    # It it an error to add a target with a name that exists in "targets.json"
-    # However, it is OK to add a target that was previously added via "add_py_targets"
-    # (this makes testing easier without changing the regular semantics)
+    # It is an error to add a target with a name that already exists.
     @staticmethod
     def add_py_targets(new_targets):
         crt_data = Target.get_json_target_data()
-        # First add all elemnts to the internal dictionary
         for tk, tv in new_targets.items():
-            if crt_data.has_key(tk) and (not tk in Target.__py_targets):
+            if crt_data.has_key(tk):
                 raise Exception("Attempt to add target '%s' that already exists" % tk)
+            # Add target data to the internal target dictionary
             crt_data[tk] = tv
-            Target.__py_targets.add(tk)
-        # Then create the new instances and update global variables if needed
-        for tk, tv in new_targets.items():
-            # Is the target already created?
-            old_target = Target.__target_map.get(tk, None)
-            # Instantiate this target. If it is public, update the data in
-            # in TARGETS, TARGET_MAP, TARGET_NAMES
+            # Create the new target and add it to the relevant data structures
             new_target = Target(tk)
-            if tv.get("public", True):
-                if old_target: # remove the old target from TARGETS and TARGET_NAMES
-                    TARGETS.remove(old_target)
-                    TARGET_NAMES.remove(tk)
-                # Add the new target
-                TARGETS.append(new_target)
-                TARGET_MAP[tk] = new_target
-                TARGET_NAMES.append(tk)
-            # Update the target cache
-            Target.__target_map[tk] = new_target
+            TARGETS.append(new_target)
+            TARGET_MAP[tk] = new_target
+            TARGET_NAMES.append(tk)
 
     # Return the target instance starting from the target name
     @staticmethod
+    @cached
     def get_target(name):
-        if not Target.__target_map.has_key(name):
-            Target.__target_map[name] = Target(name)
-        return Target.__target_map[name]
+        return Target(name)
 
     def __init__(self, name):
         self.name = name
@@ -414,3 +402,15 @@ def get_target_detect_codes():
         for detect_code in target.detect_code:
             result[detect_code] = target.name
     return result
+
+# Sets the location of the JSON file that contains the targets
+def set_targets_json_location(location):
+    # First instruct Target about the new location
+    Target.set_targets_json_location(location)
+    # Then re-initialize TARGETS, TARGET_MAP and TARGET_NAMES
+    # The re-initialization does not create new variables, it keeps the old ones instead
+    # This ensures compatibility with code that does "from tools.targets import TARGET_NAMES"
+    TARGETS[:] = [Target.get_target(name) for name, value in Target.get_json_target_data().items() if value.get("public", True)]
+    TARGET_MAP.clear()
+    TARGET_MAP.update(dict([(t.name, t) for t in TARGETS]))
+    TARGET_NAMES[:] = TARGET_MAP.keys()
diff --git a/tools/test/config_test/config_test.py b/tools/test/config_test/config_test.py
index 59c2b50c98d..d9f692e5bf8 100644
--- a/tools/test/config_test/config_test.py
+++ b/tools/test/config_test/config_test.py
@@ -16,6 +16,7 @@
 """
 
 from tools.build_api import get_config
+from tools.targets import set_targets_json_location, Target
 from tools.config import ConfigException, Config
 import os, sys
 
@@ -43,6 +44,8 @@ def test_tree(full_name, name):
         sys.stdout.flush()
         err_msg = None
         try:
+            # Use 'set_targets_json_location' to remove the previous custom targets from the target list
+            set_targets_json_location(Target._Target__targets_json_location)
             cfg, macros, features = get_config(full_name, target, "GCC_ARM")
             macros = Config.config_macros_to_macros(macros)
         except ConfigException as e: