diff --git a/python/raft-ann-bench/src/raft-ann-bench/constraints/__init__.py b/python/raft-ann-bench/src/raft-ann-bench/constraints/__init__.py
index b61d185356..e7498282aa 100644
--- a/python/raft-ann-bench/src/raft-ann-bench/constraints/__init__.py
+++ b/python/raft-ann-bench/src/raft-ann-bench/constraints/__init__.py
@@ -38,3 +38,7 @@ def raft_ivf_pq_search_constraints(params, build_params, k, batch_size):
 def raft_cagra_search_constraints(params, build_params, k, batch_size):
     if "itopk" in params:
         return params["itopk"] >= k
+
+def hnswlib_search_constraints(params, build_params, k, batch_size):
+    if "ef" in params:
+        return params["ef"] >= k
diff --git a/python/raft-ann-bench/src/raft-ann-bench/run/conf/algos/hnswlib.yaml b/python/raft-ann-bench/src/raft-ann-bench/run/conf/algos/hnswlib.yaml
index 021ca96bcd..9268c4cb08 100644
--- a/python/raft-ann-bench/src/raft-ann-bench/run/conf/algos/hnswlib.yaml
+++ b/python/raft-ann-bench/src/raft-ann-bench/run/conf/algos/hnswlib.yaml
@@ -1,8 +1,10 @@
 name: hnswlib
+constraints:
+  search: raft-ann-bench.constraints.hnswlib_search_constraints
 groups:
   base:
     build:
       M: [12, 16, 24, 36]
       efConstruction: [64, 128, 256, 512]
     search:
-      ef: [10, 20, 40, 60, 80, 120, 200, 400, 600, 800]
\ No newline at end of file
+      ef: [10, 20, 40, 60, 80, 120, 200, 400, 600, 800]