diff --git a/actors/miner/src/lib.rs b/actors/miner/src/lib.rs
index 5ee8961eb..d347a75b8 100644
--- a/actors/miner/src/lib.rs
+++ b/actors/miner/src/lib.rs
@@ -4,8 +4,8 @@
 use std::cmp::max;
 use std::collections::btree_map::Entry;
 use std::collections::{BTreeMap, BTreeSet};
-use std::iter;
 use std::ops::Neg;
+use std::{cmp, iter};
 
 use anyhow::{anyhow, Error};
 use byteorder::{BigEndian, ByteOrder, WriteBytesExt};
@@ -561,8 +561,11 @@ impl Actor {
             }
 
             // Validate that the miner didn't try to prove too many partitions at once.
-            let submission_partition_limit =
-                load_partitions_sectors_max(rt.policy(), info.window_post_partition_sectors);
+            let submission_partition_limit = cmp::min(
+                load_partitions_sectors_max(rt.policy(), info.window_post_partition_sectors),
+                rt.policy().posted_partitions_max,
+            );
+
             if params.partitions.len() as u64 > submission_partition_limit {
                 return Err(actor_error!(
                     illegal_argument,
@@ -4401,8 +4404,10 @@ struct SectorSealProofInput {
     pub sector_number: SectorNumber,
     pub randomness: SealRandomness,
     pub interactive_randomness: InteractiveSealRandomness,
-    pub sealed_cid: Cid,   // Commr
-    pub unsealed_cid: Cid, // Commd
+    // Commr
+    pub sealed_cid: Cid,
+    // Commd
+    pub unsealed_cid: Cid,
 }
 
 impl SectorSealProofInput {
diff --git a/runtime/src/runtime/policy.rs b/runtime/src/runtime/policy.rs
index d4565af6f..523b066e5 100644
--- a/runtime/src/runtime/policy.rs
+++ b/runtime/src/runtime/policy.rs
@@ -69,6 +69,9 @@ pub struct Policy {
     /// The maximum number of sector infos that may be required to be loaded in a single invocation.
     pub addressed_sectors_max: u64,
 
+    /// The maximum number of partitions that can be proven in a single PoSt message.
+    pub posted_partitions_max: u64,
+
     pub max_pre_commit_randomness_lookback: ChainEpoch,
 
     /// Number of epochs between publishing the precommit and when the challenge for interactive PoRep is drawn
@@ -173,6 +176,7 @@ impl Default for Policy {
             addressed_partitions_max: policy_constants::ADDRESSED_PARTITIONS_MAX,
             declarations_max: policy_constants::DECLARATIONS_MAX,
             addressed_sectors_max: policy_constants::ADDRESSED_SECTORS_MAX,
+            posted_partitions_max: policy_constants::POSTED_PARTITIONS_MAX,
             max_pre_commit_randomness_lookback:
                 policy_constants::MAX_PRE_COMMIT_RANDOMNESS_LOOKBACK,
             pre_commit_challenge_delay: policy_constants::PRE_COMMIT_CHALLENGE_DELAY,
@@ -271,6 +275,8 @@ pub mod policy_constants {
 
     pub const ADDRESSED_SECTORS_MAX: u64 = 25_000;
 
+    pub const POSTED_PARTITIONS_MAX: u64 = 3;
+
     pub const MAX_PRE_COMMIT_RANDOMNESS_LOOKBACK: ChainEpoch = EPOCHS_IN_DAY + CHAIN_FINALITY;
 
     #[cfg(not(feature = "short-precommit"))]