diff --git a/processing/src/main/java/org/apache/druid/segment/RowWalker.java b/processing/src/main/java/org/apache/druid/segment/RowWalker.java
index b44802481b9..2a0e2ab5a6e 100644
--- a/processing/src/main/java/org/apache/druid/segment/RowWalker.java
+++ b/processing/src/main/java/org/apache/druid/segment/RowWalker.java
@@ -35,6 +35,7 @@ public class RowWalker<T>
   private final Iterable<T> rowIterable;
   private final ToLongFunction<T> timestampFunction;
 
+  @Nullable
   private Iterator<T> rowIterator;
 
   @Nullable
@@ -60,13 +61,16 @@ public class RowWalker<T>
 
   public void advance()
   {
-    if (rowIterator.hasNext()) {
+    if (rowIterator == null) {
+      throw new IllegalStateException("cannot call advance when isDone == true");
+    } else if (rowIterator.hasNext()) {
       current = rowIterator.next();
 
       if (current == null) {
         throw new NullPointerException("null row encountered in walker");
       }
     } else {
+      rowIterator = null;
       current = null;
     }
   }
diff --git a/processing/src/main/java/org/apache/druid/segment/join/HashJoinEngine.java b/processing/src/main/java/org/apache/druid/segment/join/HashJoinEngine.java
index 40582eee77a..cdf80dcf676 100644
--- a/processing/src/main/java/org/apache/druid/segment/join/HashJoinEngine.java
+++ b/processing/src/main/java/org/apache/druid/segment/join/HashJoinEngine.java
@@ -181,6 +181,12 @@ public class HashJoinEngine
 
         assert !joinMatcher.hasMatch();
 
+        if (leftCursor.isDone()) {
+          // No right-hand matches and nothing on the left cursor. We're done; return.
+          assert isDone();
+          return;
+        }
+
         do {
           // No more right-hand side matches; advance the left-hand side.
           leftCursor.advanceUninterruptibly();