diff --git a/build/build.py b/build/build.py
index d538c7f..c66d64a 100644
--- a/build/build.py
+++ b/build/build.py
@@ -92,7 +92,7 @@ def build(
     for file in files:
         if last_build_info:
             last_build_info_for_this_file =\
-                list(filter(lambda i: i['source file'] == file.name, last_build_info['tex_sources']))
+                list(filter(lambda i: i['source file'] == str(file.relative_to(src_dir)), last_build_info['tex_sources']))
         else:
             last_build_info_for_this_file = []
         sources_to_build.append(
diff --git a/build/utils/__init__.py b/build/utils/__init__.py
index a29fb42..52a55f1 100644
--- a/build/utils/__init__.py
+++ b/build/utils/__init__.py
@@ -1,9 +1,11 @@
 from .build_information import BuildInfo
 from .pytex_file import TexFileToFormat
 from .pytex_msg import pytex_msg
+from .checksum import md5
 
 __all__ = [
     'BuildInfo',
     'TexFileToFormat',
-    'pytex_msg'
+    'pytex_msg',
+    'md5'
 ]
diff --git a/build/utils/checksum.py b/build/utils/checksum.py
new file mode 100644
index 0000000..91bf258
--- /dev/null
+++ b/build/utils/checksum.py
@@ -0,0 +1,12 @@
+import hashlib
+from pathlib import Path
+
+# https://stackoverflow.com/a/3431838/16371376
+
+
+def md5(file: Path):
+    hash_md5 = hashlib.md5()
+    with open(file, "rb") as f:
+        for block in iter(lambda: f.read(4096), b""):
+            hash_md5.update(block)
+        return hash_md5.hexdigest()
diff --git a/build/utils/pytex_file.py b/build/utils/pytex_file.py
index 07d3261..a82d132 100644
--- a/build/utils/pytex_file.py
+++ b/build/utils/pytex_file.py
@@ -5,6 +5,7 @@ from PyTeX.build.git_hook import is_recent, get_latest_commit
 from PyTeX import PackageFormatter, ClassFormatter, DictionaryFormatter
 from PyTeX.errors import *
 from .pytex_msg import pytex_msg
+from .checksum import md5
 
 from .build_information import BuildInfo
 
@@ -133,12 +134,13 @@ class TexFileToFormat:
         for written_file in written_files:
             info = {
                 'name': str(self.src_path.parent.relative_to(self.src_root)) + "/" + written_file,
-                'source file': self.src_path.name,
+                'source file': str(self.src_path.relative_to(self.src_root)),
                 'build time': self.current_build_info.build_time,
                 'source version': self.current_build_info.packages_version,
                 'source commit hash': self.current_build_info.packages_hash,
                 'pytex version': self.current_build_info.pytex_version,
                 'pytex commit hash': self.current_build_info.pytex_hash,
+                'md5sum': md5(self.build_root / self.src_path.parent.relative_to(self.src_root) / written_file),
                 'dirty': self.dirty
             }
             build_infos.append(info)