diff --git a/instrumentation/opentelemetry-instrumentation-botocore/src/opentelemetry/instrumentation/botocore/__init__.py b/instrumentation/opentelemetry-instrumentation-botocore/src/opentelemetry/instrumentation/botocore/__init__.py
index 713a1e6a61..0ec61c73fa 100644
--- a/instrumentation/opentelemetry-instrumentation-botocore/src/opentelemetry/instrumentation/botocore/__init__.py
+++ b/instrumentation/opentelemetry-instrumentation-botocore/src/opentelemetry/instrumentation/botocore/__init__.py
@@ -67,7 +67,7 @@
 def _patched_endpoint_prepare_request(wrapped, instance, args, kwargs):
     request = args[0]
     headers = request.headers
-    propagators.inject(type(headers).__setitem__, headers)
+    propagators.inject(type(headers).add_header, headers)
     return wrapped(*args, **kwargs)