diff --git a/man/man4/zfs.4 b/man/man4/zfs.4
index 04bbbc5fd..271b02b6e 100644
--- a/man/man4/zfs.4
+++ b/man/man4/zfs.4
@@ -239,6 +239,16 @@ relative to the pool.
 Make some blocks above a certain size be gang blocks.
 This option is used by the test suite to facilitate testing.
 .
+.It Sy zfs_ddt_zap_default_bs Ns = Ns Sy 15 Po 32 KiB Pc Pq int
+Default DDT ZAP data block size as a power of 2. Note that changing this after
+creating a DDT on the pool will not affect existing DDTs, only newly created
+ones.
+.
+.It Sy zfs_ddt_zap_default_ibs Ns = Ns Sy 15 Po 32 KiB Pc Pq int
+Default DDT ZAP indirect block size as a power of 2. Note that changing this
+after creating a DDT on the pool will not affect existing DDTs, only newly
+created ones.
+.
 .It Sy zfs_default_bs Ns = Ns Sy 9 Po 512 B Pc Pq int
 Default dnode block size as a power of 2.
 .
diff --git a/module/zfs/ddt_zap.c b/module/zfs/ddt_zap.c
index 27dbbc55f..8f6397a6d 100644
--- a/module/zfs/ddt_zap.c
+++ b/module/zfs/ddt_zap.c
@@ -31,8 +31,8 @@
 #include <sys/zap.h>
 #include <sys/dmu_tx.h>
 
-static const int ddt_zap_leaf_blockshift = 12;
-static const int ddt_zap_indirect_blockshift = 12;
+static unsigned int ddt_zap_default_bs = 15;
+static unsigned int ddt_zap_default_ibs = 15;
 
 static int
 ddt_zap_create(objset_t *os, uint64_t *objectp, dmu_tx_t *tx, boolean_t prehash)
@@ -43,7 +43,7 @@ ddt_zap_create(objset_t *os, uint64_t *objectp, dmu_tx_t *tx, boolean_t prehash)
 		flags |= ZAP_FLAG_PRE_HASHED_KEY;
 
 	*objectp = zap_create_flags(os, 0, flags, DMU_OT_DDT_ZAP,
-	    ddt_zap_leaf_blockshift, ddt_zap_indirect_blockshift,
+	    ddt_zap_default_bs, ddt_zap_default_ibs,
 	    DMU_OT_NONE, 0, tx);
 
 	return (*objectp == 0 ? SET_ERROR(ENOTSUP) : 0);
@@ -166,3 +166,10 @@ const ddt_ops_t ddt_zap_ops = {
 	ddt_zap_walk,
 	ddt_zap_count,
 };
+
+/* BEGIN CSTYLED */
+ZFS_MODULE_PARAM(zfs_dedup, , ddt_zap_default_bs, UINT, ZMOD_RW,
+	"DDT ZAP leaf blockshift");
+ZFS_MODULE_PARAM(zfs_dedup, , ddt_zap_default_ibs, UINT, ZMOD_RW,
+	"DDT ZAP indirect blockshift");
+/* END CSTYLED */