diff --git a/tools/targets.py b/tools/targets.py
index b203172206..1a2c3b5481 100644
--- a/tools/targets.py
+++ b/tools/targets.py
@@ -64,19 +64,22 @@ class Target:
     # 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')
+    # Default location of the 'targets.json' file
+    __targets_json_location_default = os.path.join(os.path.dirname(os.path.abspath(__file__)), '..', 'hal', 'targets.json')
+
+    # Current/new location of the 'targets.json' file
+    __targets_json_location = None
 
     # Load the description of JSON target data
     @staticmethod
     @cached
     def get_json_target_data():
-        return json_file_to_dict(Target.__targets_json_location)
+        return json_file_to_dict(Target.__targets_json_location or Target.__targets_json_location_default)
 
     # Set the location of the targets.json file
     @staticmethod
-    def set_targets_json_location(location):
-        Target.__targets_json_location = location
+    def set_targets_json_location(location=None):
+        Target.__targets_json_location = location or Target.__targets_json_location_default
         # Invalidate caches, since the location of the JSON file changed
         caches.clear()
 
@@ -410,7 +413,7 @@ def get_target_detect_codes():
     return result
 
 # Sets the location of the JSON file that contains the targets
-def set_targets_json_location(location):
+def set_targets_json_location(location=None):
     # First instruct Target about the new location
     Target.set_targets_json_location(location)
     # Then re-initialize TARGETS, TARGET_MAP and TARGET_NAMES
diff --git a/tools/toolchains/__init__.py b/tools/toolchains/__init__.py
index c6735157dd..f0b509e9af 100644
--- a/tools/toolchains/__init__.py
+++ b/tools/toolchains/__init__.py
@@ -794,6 +794,9 @@ class mbedToolchain:
                             ])
                         objects.append(result['object'])
                     except ToolException, err:
+                        if p._taskqueue.queue:
+                            p._taskqueue.queue.clear()
+                            sleep(0.5)
                         p.terminate()
                         p.join()
                         raise ToolException(err)