diff --git a/src/hnswscan.c b/src/hnswscan.c
index 61a8d63..8752d62 100644
--- a/src/hnswscan.c
+++ b/src/hnswscan.c
@@ -151,7 +151,7 @@ hnswbeginscan(Relation index, int nkeys, int norderbys)
 	/* Calculate max memory */
 	/* Add 256 extra bytes to fill last block when close */
 	maxMemory = (double) work_mem * hnsw_scan_mem_multiplier * 1024.0 + 256;
-	so->maxMemory = Min(maxMemory, (double) SIZE_MAX);
+	so->maxMemory = Min(maxMemory, (double) SIZE_MAX / 2);
 
 	scan->opaque = so;