diff --git a/config/dbscheme-fragments.json b/config/dbscheme-fragments.json
index c2a9a5e734b..a626025de0b 100644
--- a/config/dbscheme-fragments.json
+++ b/config/dbscheme-fragments.json
@@ -9,6 +9,7 @@
   "fragments": [
     "/*- Compilations -*/",
     "/*- External data -*/",
+    "/*- Overlay support -*/",
     "/*- Files and folders -*/",
     "/*- Diagnostic messages -*/",
     "/*- Diagnostic messages: severity -*/",
diff --git a/python/extractor/semmle/dbscheme.template b/python/extractor/semmle/dbscheme.template
index 07b65434bbd..43015df66f4 100644
--- a/python/extractor/semmle/dbscheme.template
+++ b/python/extractor/semmle/dbscheme.template
@@ -40,6 +40,22 @@ externalData(
   string value : string ref
 );
 
+/*- Overlay support -*/
+
+/**
+ * The CLI will automatically emit the tuple `databaseMetadata("isOverlay", "true")`,
+ * along with an `overlayChangedFiles` tuple for each new/modified/deleted file,
+ * when building an overlay database, and these can be used by the discard predicates.
+ */
+databaseMetadata(
+  string metadataKey : string ref,
+  string value : string ref
+);
+
+overlayChangedFiles(
+  string path : string ref
+);
+
 /*- DEPRECATED: Snapshot date -*/
 
 snapshotDate(unique date snapshotDate : date ref);
diff --git a/python/ql/lib/semmlecode.python.dbscheme b/python/ql/lib/semmlecode.python.dbscheme
index 5af903da088..6a1f497168d 100644
--- a/python/ql/lib/semmlecode.python.dbscheme
+++ b/python/ql/lib/semmlecode.python.dbscheme
@@ -47,6 +47,22 @@ externalData(
   string value : string ref
 );
 
+/*- Overlay support -*/
+
+/**
+ * The CLI will automatically emit the tuple `databaseMetadata("isOverlay", "true")`,
+ * along with an `overlayChangedFiles` tuple for each new/modified/deleted file,
+ * when building an overlay database, and these can be used by the discard predicates.
+ */
+databaseMetadata(
+  string metadataKey : string ref,
+  string value : string ref
+);
+
+overlayChangedFiles(
+  string path : string ref
+);
+
 /*- DEPRECATED: Snapshot date -*/
 
 snapshotDate(unique date snapshotDate : date ref);