diff --git a/mesonbuild/_typing.py b/mesonbuild/_typing.py
index 7616ad600..d3cfa39d5 100644
--- a/mesonbuild/_typing.py
+++ b/mesonbuild/_typing.py
@@ -79,42 +79,3 @@ class ImmutableListProtocol(Protocol[T]):
     def index(self, item: T) -> int: ...
 
     def copy(self) -> typing.List[T]: ...
-
-
-class ImmutableSetProtocol(Protocol[T]):
-
-    """A protocol for a set that cannot be mutated.
-
-    This provides for cases where mutation of the set is undesired. Although
-    this will be allowed at runtime, mypy (or another type checker), will see
-    any attempt to use mutative methods as an error.
-    """
-
-    def __iter__(self) -> typing.Iterator[T]: ...
-
-    def __contains__(self, item: T) -> bool: ...
-
-    def __len__(self) -> int: ...
-
-    def __add__(self, other: typing.Set[T]) -> typing.Set[T]: ...
-
-    def __eq__(self, other: typing.Any) -> bool: ...
-    def __ne__(self, other: typing.Any) -> bool: ...
-    def __le__(self, other: typing.Any) -> bool: ...
-    def __lt__(self, other: typing.Any) -> bool: ...
-    def __gt__(self, other: typing.Any) -> bool: ...
-    def __ge__(self, other: typing.Any) -> bool: ...
-
-    def copy(self) -> typing.Set[T]: ...
-
-    def difference(self, other: typing.Set[T]) -> typing.Set[T]: ...
-
-    def intersection(self, other: typing.Set[T]) -> typing.Set[T]: ...
-
-    def issubset(self, other: typing.Set[T]) -> bool: ...
-
-    def issuperset(self, other: typing.Set[T]) -> bool: ...
-
-    def symmetric_difference(self, other: typing.Set[T]) -> typing.Set[T]: ...
-
-    def union(self, other: typing.Set[T]) -> typing.Set[T]: ...
diff --git a/mesonbuild/build.py b/mesonbuild/build.py
index a5a19d992..b2f8f377c 100644
--- a/mesonbuild/build.py
+++ b/mesonbuild/build.py
@@ -47,7 +47,7 @@ from .interpreterbase import FeatureNew, FeatureDeprecated
 
 if T.TYPE_CHECKING:
     from typing_extensions import Literal
-    from ._typing import ImmutableListProtocol, ImmutableSetProtocol
+    from ._typing import ImmutableListProtocol
     from .backend.backends import Backend, ExecutableSerialisation
     from .interpreter.interpreter import Test, SourceOutputs, Interpreter
     from .interpreterbase import SubProject
@@ -1086,7 +1086,7 @@ class BuildTarget(Target):
         return result
 
     @lru_cache(maxsize=None)
-    def get_link_dep_subdirs(self) -> 'ImmutableSetProtocol[str]':
+    def get_link_dep_subdirs(self) -> T.AbstractSet[str]:
         result: OrderedSet[str] = OrderedSet()
         for i in self.link_targets:
             if not isinstance(i, StaticLibrary):
@@ -2573,7 +2573,7 @@ class CustomTarget(Target, CommandBase):
     def get_link_deps_mapping(self, prefix: str) -> T.Mapping[str, str]:
         return {}
 
-    def get_link_dep_subdirs(self):
+    def get_link_dep_subdirs(self) -> T.AbstractSet[str]:
         return OrderedSet()
 
     def get_all_link_deps(self):
@@ -2765,7 +2765,7 @@ class CustomTargetIndex(HoldableObject):
     def get_link_deps_mapping(self, prefix: str) -> T.Mapping[str, str]:
         return self.target.get_link_deps_mapping(prefix)
 
-    def get_link_dep_subdirs(self):
+    def get_link_dep_subdirs(self) -> T.AbstractSet[str]:
         return self.target.get_link_dep_subdirs()
 
     def is_linkable_target(self) -> bool: