diff --git a/HISTORY.rst b/HISTORY.rst
index 80144ad7..2e10451e 100644
--- a/HISTORY.rst
+++ b/HISTORY.rst
@@ -23,6 +23,8 @@ PlatformIO 3.0
   - CLion: Improved project portability using "${CMAKE_CURRENT_LIST_DIR}" instead of full path
 
 * Fixed an issue with incorrect detecting of compatibility (LDF) between generic library and Arduino or ARM mbed frameworks
+* Fixed "Runtime Error: Dictionary size changed during iteration"
+  (`issue #2003 <https://github.com/platformio/platformio-core/issues/2003>`_)
 
 3.6.3 (2018-12-12)
 ~~~~~~~~~~~~~~~~~~
diff --git a/platformio/telemetry.py b/platformio/telemetry.py
index 9d379c23..1ced1f7d 100644
--- a/platformio/telemetry.py
+++ b/platformio/telemetry.py
@@ -388,7 +388,7 @@ def backup_reports(items):
 
     for params in items:
         # skip static options
-        for key in params:
+        for key in params.keys():
             if key in ("v", "tid", "cid", "cd1", "cd2", "sr", "an"):
                 del params[key]