diff --git a/mesonbuild/depfile.py b/mesonbuild/depfile.py
index 62cbe8125..a8b458823 100644
--- a/mesonbuild/depfile.py
+++ b/mesonbuild/depfile.py
@@ -11,12 +11,13 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import collections
+import typing as T
 
-def parse(lines):
-    rules = []
-    targets = []
-    deps = []
+
+def parse(lines: T.Iterable[str]) -> T.List[T.Tuple[T.List[str], T.List[str]]]:
+    rules: T.List[T.Tuple[T.List[str], T.List[str]]] = []
+    targets: T.List[str] = []
+    deps: T.List[str] = []
     in_deps = False
     out = ''
     for line in lines:
@@ -56,12 +57,15 @@ def parse(lines):
             out += c
     return rules
 
-Target = collections.namedtuple('Target', ['deps'])
+class Target(T.NamedTuple):
+
+    deps: T.Set[str]
+
 
 class DepFile:
-    def __init__(self, lines):
+    def __init__(self, lines: T.Iterable[str]):
         rules = parse(lines)
-        depfile = {}
+        depfile: T.Dict[str, Target] = {}
         for (targets, deps) in rules:
             for target in targets:
                 t = depfile.setdefault(target, Target(deps=set()))
@@ -69,16 +73,17 @@ class DepFile:
                     t.deps.add(dep)
         self.depfile = depfile
 
-    def get_all_dependencies(self, target, visited=None):
-        deps = set()
+    def get_all_dependencies(self, name: str, visited: T.Optional[T.Set[str]] = None) -> T.List[str]:
+        deps: T.Set[str] = set()
         if not visited:
             visited = set()
-        if target in visited:
-            return set()
-        visited.add(target)
-        target = self.depfile.get(target)
+        if name in visited:
+            return []
+        visited.add(name)
+
+        target = self.depfile.get(name)
         if not target:
-            return set()
+            return []
         deps.update(target.deps)
         for dep in target.deps:
             deps.update(self.get_all_dependencies(dep, visited))
diff --git a/run_mypy.py b/run_mypy.py
index 1c2d64498..1c2759a52 100755
--- a/run_mypy.py
+++ b/run_mypy.py
@@ -25,6 +25,7 @@ modules = [
     'mesonbuild/arglist.py',
     'mesonbuild/backend/backends.py',
     # 'mesonbuild/coredata.py',
+    'mesonbuild/depfile.py',
     'mesonbuild/envconfig.py',
     'mesonbuild/interpreter/compiler.py',
     'mesonbuild/interpreter/mesonmain.py',