diff --git a/poetry/utils/exporter.py b/poetry/utils/exporter.py
index 5f2d6303817..f7c40f6975f 100644
--- a/poetry/utils/exporter.py
+++ b/poetry/utils/exporter.py
@@ -7,6 +7,7 @@
 from poetry.poetry import Poetry
 from poetry.utils._compat import Path
 from poetry.utils._compat import decode
+from poetry.utils._compat import urlparse
 
 
 class Exporter(object):
@@ -139,6 +140,9 @@ def _export_requirements_txt(
                 url = (
                     repository.authenticated_url if with_credentials else repository.url
                 )
+                parsed_url = urlparse.urlsplit(url)
+                if parsed_url.scheme == "http":
+                    indexes_header += "--trusted-host {}\n".format(parsed_url.netloc)
                 indexes_header += "--extra-index-url {}\n".format(url)
 
             content = indexes_header + "\n" + content
diff --git a/tests/utils/test_exporter.py b/tests/utils/test_exporter.py
index d810bb8b08b..c5ce0214ff7 100644
--- a/tests/utils/test_exporter.py
+++ b/tests/utils/test_exporter.py
@@ -972,6 +972,52 @@ def test_exporter_exports_requirements_txt_with_legacy_packages(tmp_dir, poetry)
     assert expected == content
 
 
+def test_exporter_exports_requirements_txt_with_legacy_packages_trusted_host(
+    tmp_dir, poetry
+):
+    poetry.pool.add_repository(LegacyRepository("custom", "http://example.com/simple",))
+    poetry.locker.mock_lock_data(
+        {
+            "package": [
+                {
+                    "name": "bar",
+                    "version": "4.5.6",
+                    "category": "dev",
+                    "optional": False,
+                    "python-versions": "*",
+                    "source": {
+                        "type": "legacy",
+                        "url": "http://example.com/simple",
+                        "reference": "",
+                    },
+                },
+            ],
+            "metadata": {
+                "python-versions": "*",
+                "content-hash": "123456789",
+                "hashes": {"bar": ["67890"]},
+            },
+        }
+    )
+    set_package_requires(poetry)
+    exporter = Exporter(poetry)
+
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt", dev=True)
+
+    with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
+        content = f.read()
+
+    expected = """\
+--trusted-host example.com
+--extra-index-url http://example.com/simple
+
+bar==4.5.6 \\
+    --hash=sha256:67890
+"""
+
+    assert expected == content
+
+
 @pytest.mark.parametrize(
     ("dev", "expected"),
     [