diff --git a/src/poetry/packages/locker.py b/src/poetry/packages/locker.py
index 6b3317a0795..249d2e157d8 100644
--- a/src/poetry/packages/locker.py
+++ b/src/poetry/packages/locker.py
@@ -236,16 +236,16 @@ def __walk_dependency_level(
             if locked_package:
                 # create dependency from locked package to retain dependency metadata
                 # if this is not done, we can end-up with incorrect nested dependencies
+                constraint = requirement.constraint
+                pretty_constraint = requirement.pretty_constraint
                 marker = requirement.marker
                 requirement = locked_package.to_dependency()
                 requirement.marker = requirement.marker.intersect(marker)
 
-                key = (requirement.name, requirement.pretty_constraint)
+                key = (requirement.name, pretty_constraint)
 
-                if pinned_versions:
-                    requirement.set_constraint(
-                        locked_package.to_dependency().constraint
-                    )
+                if not pinned_versions:
+                    requirement.set_constraint(constraint)
 
                 for require in locked_package.requires:
                     if require.marker.is_empty():
diff --git a/src/poetry/utils/exporter.py b/src/poetry/utils/exporter.py
index 08a3c8dd60a..98070d19b23 100644
--- a/src/poetry/utils/exporter.py
+++ b/src/poetry/utils/exporter.py
@@ -1,3 +1,4 @@
+import itertools
 import urllib.parse
 
 from typing import TYPE_CHECKING
@@ -69,13 +70,21 @@ def _export_requirements_txt(
         content = ""
         dependency_lines = set()
 
-        for dependency_package in self._poetry.locker.get_project_dependency_packages(
-            project_requires=self._poetry.package.all_requires, dev=dev, extras=extras
+        for package, groups in itertools.groupby(
+            self._poetry.locker.get_project_dependency_packages(
+                project_requires=self._poetry.package.all_requires,
+                dev=dev,
+                extras=extras,
+            ),
+            lambda dependency_package: dependency_package.package,
         ):
             line = ""
-
-            dependency = dependency_package.dependency
-            package = dependency_package.package
+            dependency_packages = list(groups)
+            dependency = dependency_packages[0].dependency
+            marker = dependency.marker
+            for dep_package in dependency_packages[1:]:
+                marker = marker.union(dep_package.dependency.marker)
+            dependency.marker = marker
 
             if package.develop:
                 line += "-e "