diff --git a/src/wily/commands/build.py b/src/wily/commands/build.py
index a365290f..f7e8aff4 100644
--- a/src/wily/commands/build.py
+++ b/src/wily/commands/build.py
@@ -7,6 +7,7 @@
 import multiprocessing
 import os
 import pathlib
+from collections.abc import Sequence
 from sys import exit
 from typing import Any, Dict, List, Tuple
 
@@ -39,6 +40,7 @@ def run_operator(
     # Normalize paths for non-seed passes
     for key in list(data.keys()):
         if os.path.isabs(key):
+            # ToDo: Handle paths on different drives in Windows
             rel = os.path.relpath(key, config.path)
             data[rel] = data[key]
             del data[key]
@@ -95,17 +97,26 @@ def build(config: WilyConfig, archiver: Archiver, operators: List[Operator]) ->
     try:
         with multiprocessing.Pool(processes=len(operators)) as pool:
             prev_stats: Dict[str, Dict] = {}
+            assert isinstance(config.targets, Sequence)
+            resolved_path = pathlib.Path(config.path).resolve()
+            resolved_targets = [
+                pathlib.Path(target).resolve() for target in config.targets
+            ]
             for revision in revisions:
                 # Checkout target revision
                 archiver_instance.checkout(revision, config.checkout_options)
                 stats: Dict[str, Dict] = {"operator_data": {}}
 
-                # TODO : Check that changed files are children of the targets
                 targets = [
                     str(pathlib.Path(config.path) / pathlib.Path(file))
                     for file in revision.added_files + revision.modified_files
-                    # if any([True for target in config.targets if
-                    #         target in pathlib.Path(pathlib.Path(config.path) / pathlib.Path(file)).parents])
+                    if config.targets == ["."]  # Add all files if no target is set
+                    # Check that changed files are children of the targets
+                    or any(
+                        True
+                        for target in resolved_targets
+                        if target in (resolved_path / file).parents
+                    )
                 ]
 
                 # Run each operator as a separate process
diff --git a/test/unit/test_build_unit.py b/test/unit/test_build_unit.py
index ddd8fb86..8dc828e6 100644
--- a/test/unit/test_build_unit.py
+++ b/test/unit/test_build_unit.py
@@ -1,6 +1,7 @@
 import os
+import pathlib
 import sys
-from unittest.mock import patch
+from unittest.mock import MagicMock, patch
 
 import pytest
 
@@ -38,7 +39,7 @@ def revisions(self, path, max_revisions):
                 message="None again",
                 tracked_files=["a", "b", "c", "d"],
                 tracked_dirs=["d"],
-                added_files=["e"],
+                added_files=["e", "d/h"],
                 modified_files=["f"],
                 deleted_files=["a"],
             ),
@@ -50,7 +51,7 @@ def checkout(self, revision, options):
 
 class MockOperatorCls(BaseOperator):
     name = "test"
-    data = {"C:\\home\\test1.py" if sys.platform == "win32" else "/home/test1.py": None}
+    data = {"\\home\\test1.py" if sys.platform == "win32" else "/home/test1.py": None}
 
     def __init__(self, *args, **kwargs):
         pass
@@ -72,6 +73,11 @@ def config():
 
 def test_build_simple(config):
     _test_operators = (MockOperator,)
+    # Remove drive from config path, as that breaks os.path.relpath on GitHub
+    # test runner because config path and test directory point to different drives
+    path = config.path
+    config.path = str(pathlib.Path().joinpath("/", *pathlib.Path(path).parts[1:]))
+
     with patch("wily.state.resolve_archiver", return_value=MockArchiver), patch(
         "wily.commands.build.resolve_operator", return_value=MockOperator
     ):
@@ -79,9 +85,47 @@ def test_build_simple(config):
     assert result is None
 
 
+def test_build_targets():
+    mock_state = MagicMock()
+    mock_starmap = MagicMock()
+    mock_pool = MagicMock()
+    mock_pool.return_value = mock_pool
+    mock_pool.__enter__.return_value = mock_pool
+    mock_pool.starmap = mock_starmap
+
+    config = DEFAULT_CONFIG
+    config.path = "."
+    _test_operators = (MockOperator,)
+    d_path = pathlib.Path("d/")
+    h_path = str(d_path / "h")
+
+    config.targets = ["."]
+    with patch("wily.state.resolve_archiver", return_value=MockArchiver), patch(
+        "wily.commands.build.resolve_operator", return_value=MockOperator
+    ), patch("wily.commands.build.State", mock_state), patch(
+        "wily.commands.build.multiprocessing.Pool", mock_pool
+    ):
+        build.build(config, MockArchiver, _test_operators)  # type: ignore
+    assert len(mock_starmap.mock_calls) == 6
+    assert mock_starmap.call_args_list[0][0][1][-1][-1] == ["e", h_path, "f"]
+    assert mock_starmap.call_args_list[1][0][1][-1][-1] == []
+
+    config.targets = [str(d_path)]
+    mock_starmap.reset_mock()
+    with patch("wily.state.resolve_archiver", return_value=MockArchiver), patch(
+        "wily.commands.build.resolve_operator", return_value=MockOperator
+    ), patch("wily.commands.build.State", mock_state), patch(
+        "wily.commands.build.multiprocessing.Pool", mock_pool
+    ):
+        build.build(config, MockArchiver, _test_operators)  # type: ignore
+    assert len(mock_starmap.mock_calls) == 6
+    assert mock_starmap.call_args_list[0][0][1][-1][-1] == [h_path]
+    assert mock_starmap.call_args_list[1][0][1][-1][-1] == []
+
+
 def test_run_operator(config):
     rev = Revision("123", None, None, 1, "message", [], [], [], [], [])
     name, data = build.run_operator(MockOperator, rev, config, ["test1.py"])
     assert name == "mock"
-    path = "C:\\home\\test1.py" if sys.platform == "win32" else "/home/test1.py"
+    path = "\\home\\test1.py" if sys.platform == "win32" else "/home/test1.py"
     assert data == {os.path.relpath(path, config.path): None}