diff --git a/source/extensions/filters/http/ext_authz/ext_authz.cc b/source/extensions/filters/http/ext_authz/ext_authz.cc
index c7b4bb98779a7..cd366c8f0de32 100644
--- a/source/extensions/filters/http/ext_authz/ext_authz.cc
+++ b/source/extensions/filters/http/ext_authz/ext_authz.cc
@@ -31,6 +31,10 @@ void FilterConfigPerRoute::merge(const FilterConfigPerRoute& other) {
 }
 
 void Filter::initiateCall(const Http::HeaderMap& headers) {
+  if (filter_return_ == FilterReturn::StopDecoding) {
+    return;
+  }
+
   Router::RouteConstSharedPtr route = callbacks_->route();
   if (route == nullptr || route->routeEntry() == nullptr) {
     return;
@@ -96,8 +100,10 @@ Http::FilterHeadersStatus Filter::decodeHeaders(Http::HeaderMap& headers, bool e
 
 Http::FilterDataStatus Filter::decodeData(Buffer::Instance&, bool end_stream) {
   if (buffer_data_) {
-    if (end_stream || isBufferFull()) {
-      ENVOY_STREAM_LOG(debug, "ext_authz filter finished buffering the request", *callbacks_);
+    const bool buffer_is_full = isBufferFull();
+    if (end_stream || buffer_is_full) {
+      ENVOY_STREAM_LOG(debug, "ext_authz filter finished buffering the request since {}",
+                       *callbacks_, buffer_is_full ? "buffer is full" : "stream is ended");
       initiateCall(*request_headers_);
       return filter_return_ == FilterReturn::StopDecoding
                  ? Http::FilterDataStatus::StopIterationAndWatermark
diff --git a/test/extensions/filters/http/ext_authz/ext_authz_test.cc b/test/extensions/filters/http/ext_authz/ext_authz_test.cc
index e011340c5a16b..df2af91180eef 100644
--- a/test/extensions/filters/http/ext_authz/ext_authz_test.cc
+++ b/test/extensions/filters/http/ext_authz/ext_authz_test.cc
@@ -328,7 +328,11 @@ TEST_F(HttpFilterTest, RequestDataWithPartialMessage) {
   EXPECT_EQ(Http::FilterDataStatus::StopIterationAndBuffer, filter_->decodeData(data_, false));
 
   data_.add("barfoo");
+  EXPECT_EQ(Http::FilterDataStatus::StopIterationAndWatermark, filter_->decodeData(data_, false));
+
+  data_.add("more data after watermark is set is possible");
   EXPECT_EQ(Http::FilterDataStatus::StopIterationAndWatermark, filter_->decodeData(data_, true));
+
   EXPECT_EQ(Http::FilterTrailersStatus::StopIteration, filter_->decodeTrailers(request_headers_));
 }