diff --git a/poetry/packages/locker.py b/poetry/packages/locker.py
index 2b696b3450a..2283a2373d2 100644
--- a/poetry/packages/locker.py
+++ b/poetry/packages/locker.py
@@ -182,9 +182,9 @@ def locked_repository(
         return packages
 
     def get_project_dependencies(
-        self, project_requires, pinned_versions=False, with_nested=False
-    ):  # type: (List[Dependency], bool, bool) -> Any
-        packages = self.locked_repository().packages
+        self, project_requires, pinned_versions=False, with_nested=False, with_dev=False
+    ):  # type: (List[Dependency], bool, bool, bool) -> Any
+        packages = self.locked_repository(with_dev).packages
 
         # group packages entries by name, this is required because requirement might use
         # different constraints
@@ -230,6 +230,10 @@ def __get_locked_package(
                     # project level dependencies take precedence
                     continue
 
+                # we make a copy to avoid any side-effects
+                requirement = deepcopy(requirement)
+                requirement._category = pkg.category
+
                 if pinned_versions:
                     requirement.set_constraint(
                         __get_locked_package(requirement).to_dependency().constraint
diff --git a/poetry/utils/exporter.py b/poetry/utils/exporter.py
index 19b48452346..ee8e751f95b 100644
--- a/poetry/utils/exporter.py
+++ b/poetry/utils/exporter.py
@@ -68,12 +68,14 @@ def _export_requirements_txt(
         dependency_lines = set()
 
         for dependency in self._poetry.locker.get_project_dependencies(
-            project_requires=self._poetry.package.requires
-            if not dev
-            else self._poetry.package.all_requires,
+            project_requires=self._poetry.package.all_requires,
             with_nested=True,
+            with_dev=dev,
         ):
-            package = repository.find_packages(dependency=dependency)[0]
+            try:
+                package = repository.find_packages(dependency=dependency)[0]
+            except IndexError:
+                continue
 
             # If a package is optional and we haven't opted in to it, continue
             if package.optional and package.name not in extra_package_names:
diff --git a/tests/utils/test_exporter.py b/tests/utils/test_exporter.py
index c2eee0d1f11..e26f448f6de 100644
--- a/tests/utils/test_exporter.py
+++ b/tests/utils/test_exporter.py
@@ -779,6 +779,68 @@ def test_exporter_exports_requirements_txt_with_legacy_packages(tmp_dir, poetry)
     assert expected == content
 
 
+@pytest.mark.parametrize(
+    ("dev", "expected"),
+    [
+        (True, ["bar==1.2.2", "baz==1.2.3", "foo==1.2.1"]),
+        (False, ["bar==1.2.2", "foo==1.2.1"]),
+    ],
+)
+def test_exporter_exports_requirements_txt_with_dev_extras(
+    tmp_dir, poetry, dev, expected
+):
+    poetry.locker.mock_lock_data(
+        {
+            "package": [
+                {
+                    "name": "foo",
+                    "version": "1.2.1",
+                    "category": "main",
+                    "optional": False,
+                    "python-versions": "*",
+                },
+                {
+                    "name": "bar",
+                    "version": "1.2.2",
+                    "category": "main",
+                    "optional": False,
+                    "python-versions": "*",
+                    "dependencies": {
+                        "baz": {
+                            "version": ">=0.1.0",
+                            "optional": True,
+                            "markers": "extra == 'baz'",
+                        }
+                    },
+                    "extras": {"baz": ["baz (>=0.1.0)"]},
+                },
+                {
+                    "name": "baz",
+                    "version": "1.2.3",
+                    "category": "dev",
+                    "optional": False,
+                    "python-versions": "*",
+                },
+            ],
+            "metadata": {
+                "python-versions": "*",
+                "content-hash": "123456789",
+                "hashes": {"foo": [], "bar": [], "baz": []},
+            },
+        }
+    )
+    set_package_requires(poetry)
+
+    exporter = Exporter(poetry)
+
+    exporter.export("requirements.txt", Path(tmp_dir), "requirements.txt", dev=dev)
+
+    with (Path(tmp_dir) / "requirements.txt").open(encoding="utf-8") as f:
+        content = f.read()
+
+    assert content == "{}\n".format("\n".join(expected))
+
+
 def test_exporter_exports_requirements_txt_with_legacy_packages_and_duplicate_sources(
     tmp_dir, poetry
 ):