diff --git a/src/beet/toolchain/project.py b/src/beet/toolchain/project.py
index 4c5c35cbd..9fd90ab13 100644
--- a/src/beet/toolchain/project.py
+++ b/src/beet/toolchain/project.py
@@ -104,12 +104,21 @@ def cache(self) -> ProjectCache:
 
     @property
     def ignore(self) -> List[str]:
-        ignore = list(self.config.ignore)
+        ignore = set(self.config.ignore)
         if self.output_directory and self.directory in self.output_directory.parents:
-            ignore.append(
+            ignore.add(
                 f"{self.output_directory.relative_to(self.directory).as_posix()}/"
             )
-        return ignore
+        for entry in self.config.pipeline:
+            if isinstance(entry, ProjectConfig):
+                ignore.update(entry.ignore)
+                if entry.output:
+                    output_directory = Path(entry.output)
+                    if entry.directory in output_directory.parents:
+                        ignore.add(
+                            f"{output_directory.relative_to(entry.directory).as_posix()}/"
+                        )
+        return list(ignore)
 
     @property
     def worker_pool(self):