diff --git a/python/deptry/module.py b/python/deptry/module.py
index c9b1aa8f..2ae48b88 100644
--- a/python/deptry/module.py
+++ b/python/deptry/module.py
@@ -3,6 +3,7 @@
 import logging
 from dataclasses import dataclass, field
 from importlib.metadata import PackageNotFoundError, metadata
+from importlib.util import find_spec
 from typing import TYPE_CHECKING
 
 if TYPE_CHECKING:
@@ -118,10 +119,16 @@ def _get_package_name_from_metadata(self) -> str | None:
         try:
             name: str = metadata(self.name)["Name"]
         except PackageNotFoundError:
-            return None
+            return self.name if self._is_package_installed() else None
         else:
             return name
 
+    def _is_package_installed(self) -> bool:
+        try:
+            return find_spec(self.name) is not None
+        except (ModuleNotFoundError, ValueError):
+            return False
+
     def _get_corresponding_top_levels_from(self, dependencies: list[Dependency]) -> list[str]:
         """
         Not all modules have associated metadata. e.g. `mpl_toolkits` from `matplotlib` has no metadata. However, it is
diff --git a/tests/fixtures/project_with_requirements_in/requirements.in b/tests/fixtures/project_with_requirements_in/requirements.in
index 040fb4a8..39a3d717 100644
--- a/tests/fixtures/project_with_requirements_in/requirements.in
+++ b/tests/fixtures/project_with_requirements_in/requirements.in
@@ -2,3 +2,4 @@ click==8.1.7
 isort==5.13.2
 urllib3==2.2.3
 uvicorn==0.32.0
+itchiodl==2.3.0
diff --git a/tests/fixtures/project_with_requirements_in/requirements.txt b/tests/fixtures/project_with_requirements_in/requirements.txt
index b47a71bc..f2afe44a 100644
--- a/tests/fixtures/project_with_requirements_in/requirements.txt
+++ b/tests/fixtures/project_with_requirements_in/requirements.txt
@@ -4,15 +4,35 @@
 #
 #    pip-compile
 #
-click==8.1.8
+args==0.1.0
+    # via clint
+beautifulsoup4==4.12.3
+    # via itchiodl
+certifi==2024.12.14
+    # via requests
+charset-normalizer==3.4.1
+    # via requests
+click==8.1.7
     # via
     #   -r requirements.in
     #   uvicorn
+clint==0.5.1
+    # via itchiodl
 h11==0.14.0
     # via uvicorn
+idna==3.10
+    # via requests
 isort==5.13.2
     # via -r requirements.in
-urllib3==2.3.0
+itchiodl==2.3.0
     # via -r requirements.in
-uvicorn==0.34.0
+requests==2.32.3
+    # via itchiodl
+soupsieve==2.6
+    # via beautifulsoup4
+urllib3==2.2.3
+    # via
+    #   -r requirements.in
+    #   requests
+uvicorn==0.32.0
     # via -r requirements.in
diff --git a/tests/fixtures/project_with_requirements_in/src/main.py b/tests/fixtures/project_with_requirements_in/src/main.py
index 2a252b33..f93efead 100644
--- a/tests/fixtures/project_with_requirements_in/src/main.py
+++ b/tests/fixtures/project_with_requirements_in/src/main.py
@@ -6,3 +6,5 @@
 import h11
 import white as w
 from urllib3 import contrib
+import bs4
+import itchiodl
diff --git a/tests/functional/cli/test_cli_requirements_in.py b/tests/functional/cli/test_cli_requirements_in.py
index 2c615051..a73f3056 100644
--- a/tests/functional/cli/test_cli_requirements_in.py
+++ b/tests/functional/cli/test_cli_requirements_in.py
@@ -56,6 +56,11 @@ def test_cli_single_requirements_files(pip_venv_factory: PipVenvFactory) -> None
                 "module": "white",
                 "location": {"file": str(Path("src/main.py")), "line": 7, "column": 8},
             },
+            {
+                "error": {"code": "DEP003", "message": "'bs4' imported but it is a transitive dependency"},
+                "module": "bs4",
+                "location": {"file": str(Path("src/main.py")), "line": 9, "column": 8},
+            },
             {
                 "error": {"code": "DEP001", "message": "'arrow' imported but missing from the dependency definitions"},
                 "module": "arrow",
@@ -80,11 +85,58 @@ def test_cli_multiple_requirements_files(pip_venv_factory: PipVenvFactory) -> No
 
         assert result.returncode == 1
         assert get_issues_report(Path(issue_report)) == [
+            {
+                "error": {"code": "DEP002", "message": "'args' defined as a dependency but not used in the codebase"},
+                "module": "args",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
+            {
+                "error": {
+                    "code": "DEP002",
+                    "message": "'certifi' defined as a dependency but not used in the codebase",
+                },
+                "module": "certifi",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
+            {
+                "error": {
+                    "code": "DEP002",
+                    "message": "'charset-normalizer' defined as a dependency but not used in the codebase",
+                },
+                "module": "charset-normalizer",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
+            {
+                "error": {"code": "DEP002", "message": "'clint' defined as a dependency but not used in the codebase"},
+                "module": "clint",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
+            {
+                "error": {"code": "DEP002", "message": "'idna' defined as a dependency but not used in the codebase"},
+                "module": "idna",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
             {
                 "error": {"code": "DEP002", "message": "'isort' defined as a dependency but not used in the codebase"},
                 "module": "isort",
                 "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
             },
+            {
+                "error": {
+                    "code": "DEP002",
+                    "message": "'requests' defined as a dependency but not used in the codebase",
+                },
+                "module": "requests",
+                "location": {"file": str(Path("requirements.txt")), "line": None, "column": None},
+            },
+            {
+                "error": {
+                    "code": "DEP002",
+                    "message": "'soupsieve' defined as a dependency but not used in the codebase",
+                },
+                "module": "soupsieve",
+                "location": {"file": "requirements.txt", "line": None, "column": None},
+            },
             {
                 "error": {
                     "code": "DEP002",
diff --git a/tests/unit/test_module.py b/tests/unit/test_module.py
index 63e91a7a..864b5c47 100644
--- a/tests/unit/test_module.py
+++ b/tests/unit/test_module.py
@@ -1,6 +1,10 @@
 from __future__ import annotations
 
+from importlib.metadata import PackageNotFoundError
 from pathlib import Path
+from unittest.mock import patch
+
+import pytest
 
 from deptry.dependency import Dependency
 from deptry.module import ModuleBuilder
@@ -35,3 +39,40 @@ def test_local_module() -> None:
     assert module.package is None
     assert module.standard_library is False
     assert module.local_module is True
+
+
+def test_transitive_module() -> None:
+    with (
+        patch("deptry.module.metadata", side_effect=PackageNotFoundError),
+        patch("deptry.module.find_spec", return_value="bar"),
+    ):
+        module = ModuleBuilder("foo", set(), frozenset()).build()
+
+    assert module.package == "foo"
+    assert module.standard_library is False
+    assert module.local_module is False
+
+
+def test_transitive_module_no_spec() -> None:
+    with (
+        patch("deptry.module.metadata", side_effect=PackageNotFoundError),
+        patch("deptry.module.find_spec", return_value=None),
+    ):
+        module = ModuleBuilder("foo", set(), frozenset()).build()
+
+    assert module.package is None
+    assert module.standard_library is False
+    assert module.local_module is False
+
+
+@pytest.mark.parametrize("exception", [ModuleNotFoundError, ValueError])
+def test_transitive_module_spec_error(exception: Exception) -> None:
+    with (
+        patch("deptry.module.metadata", side_effect=PackageNotFoundError),
+        patch("deptry.module.find_spec", side_effect=exception),
+    ):
+        module = ModuleBuilder("foo", set(), frozenset()).build()
+
+    assert module.package is None
+    assert module.standard_library is False
+    assert module.local_module is False