diff --git a/src/hnswbuild.c b/src/hnswbuild.c
index b667478b..89c96ca7 100644
--- a/src/hnswbuild.c
+++ b/src/hnswbuild.c
@@ -45,6 +45,7 @@
 #include "access/xloginsert.h"
 #include "catalog/index.h"
 #include "catalog/pg_type_d.h"
+#include "cdb/cdbvars.h"
 #include "commands/progress.h"
 #include "hnsw.h"
 #include "miscadmin.h"
@@ -1037,6 +1038,15 @@ ComputeParallelWorkers(Relation heap, Relation index)
 {
 	int			parallel_workers;
 
+	/*
+	 * Follow index_build(): parallel workers launched on the QD inherit
+	 * QE-only interconnect state (ic_htab_size, numsegmentsFromQD) that is
+	 * unset in a dispatcher backend, so disable parallelism on the QD and
+	 * for AO tables just like the core btree build path does.
+	 */
+	if (Gp_role == GP_ROLE_DISPATCH || AMHandlerIsAO(heap->rd_amhandler))
+		return 0;
+
 	/* Make sure it's safe to use parallel workers */
 	parallel_workers = plan_create_index_workers(RelationGetRelid(heap), RelationGetRelid(index));
 	if (parallel_workers == 0)
diff --git a/src/ivfbuild.c b/src/ivfbuild.c
index ee2afd40..b8ab09a9 100644
--- a/src/ivfbuild.c
+++ b/src/ivfbuild.c
@@ -934,8 +934,14 @@ AssignTuples(IvfflatBuildState * buildstate)
 
 	pgstat_progress_update_param(PROGRESS_CREATEIDX_SUBPHASE, PROGRESS_IVFFLAT_PHASE_ASSIGN);
 
-	/* Calculate parallel workers */
-	if (buildstate->heap != NULL)
+	/*
+	 * Follow index_build(): parallel workers launched on the QD inherit
+	 * QE-only interconnect state (ic_htab_size, numsegmentsFromQD) that is
+	 * unset in a dispatcher backend, so disable parallelism on the QD and
+	 * for AO tables just like the core btree build path does.
+	 */
+	if (buildstate->heap != NULL && Gp_role != GP_ROLE_DISPATCH &&
+		!AMHandlerIsAO(buildstate->heap->rd_amhandler))
 		parallel_workers = plan_create_index_workers(RelationGetRelid(buildstate->heap), RelationGetRelid(buildstate->index));
 
 	/* Attempt to launch parallel worker scan when required */