diff --git a/tools/makemanifest.py b/tools/makemanifest.py
index a8b310ad65..2cee6aebc7 100644
--- a/tools/makemanifest.py
+++ b/tools/makemanifest.py
@@ -235,6 +235,9 @@ def main():
     # Get paths to tools
     MAKE_FROZEN = VARS["MPY_DIR"] + "/tools/make-frozen.py"
     MPY_CROSS = VARS["MPY_DIR"] + "/mpy-cross/mpy-cross"
+    if sys.platform == "win32":
+        MPY_CROSS += ".exe"
+    MPY_CROSS = os.getenv("MICROPY_MPYCROSS", MPY_CROSS)
     MPY_TOOL = VARS["MPY_DIR"] + "/tools/mpy-tool.py"
 
     # Ensure mpy-cross is built