diff --git a/src/execution/source_indexer.rs b/src/execution/source_indexer.rs
index d720786e..33b8198e 100644
--- a/src/execution/source_indexer.rs
+++ b/src/execution/source_indexer.rs
@@ -278,11 +278,14 @@ impl SourceIndexingContext {
         let deleted_key_versions = {
             let mut deleted_key_versions = Vec::new();
             let mut state = self.state.lock().unwrap();
-            for (key, row_state) in state.rows.iter_mut() {
+            for (key, row_state) in state.rows.iter() {
                 if row_state.touched_generation < scan_generation {
                     deleted_key_versions.push((key.clone(), row_state.source_version.ordinal));
                 }
             }
+            for (key, _) in deleted_key_versions.iter() {
+                state.rows.remove(key);
+            }
             deleted_key_versions
         };
         for (key, source_ordinal) in deleted_key_versions {