diff --git a/piptools/scripts/options.py b/piptools/scripts/options.py
index 98fbbf7a1..6ae9916df 100644
--- a/piptools/scripts/options.py
+++ b/piptools/scripts/options.py
@@ -295,6 +295,7 @@ def _get_default_option(option_name: str) -> Any:
     "--emit-index-url/--no-emit-index-url",
     is_flag=True,
     default=True,
+    envvar="PIP_TOOLS_EMIT_INDEX_URL",
     help="Add index URL to generated file",
 )