diff --git a/cumulus/polkadot-parachains/rococo-runtime/src/lib.rs b/cumulus/polkadot-parachains/rococo-runtime/src/lib.rs
index b2ede43709255cf12b33bf925d7f06b900201bab..f310d8920f100ce59d645fc02c01a9696386d978 100644
--- a/cumulus/polkadot-parachains/rococo-runtime/src/lib.rs
+++ b/cumulus/polkadot-parachains/rococo-runtime/src/lib.rs
@@ -119,8 +119,8 @@ const AVERAGE_ON_INITIALIZE_RATIO: Perbill = Perbill::from_percent(10);
 /// We allow `Normal` extrinsics to fill up the block up to 75%, the rest can be used
 /// by  Operational  extrinsics.
 const NORMAL_DISPATCH_RATIO: Perbill = Perbill::from_percent(75);
-/// We allow for 2 seconds of compute with a 6 second average block time.
-const MAXIMUM_BLOCK_WEIGHT: Weight = 2 * WEIGHT_PER_SECOND;
+/// We allow for .5 seconds of compute with a 12 second average block time.
+const MAXIMUM_BLOCK_WEIGHT: Weight = WEIGHT_PER_SECOND / 2;
 
 parameter_types! {
 	pub const BlockHashCount: BlockNumber = 250;
diff --git a/cumulus/polkadot-parachains/shell-runtime/src/lib.rs b/cumulus/polkadot-parachains/shell-runtime/src/lib.rs
index bc8b0e170ce9861e5b2bb57e40d7e78be31b92c4..b6ab4b16d67ebfbe72a9d68ef5a801662c7f7a65 100644
--- a/cumulus/polkadot-parachains/shell-runtime/src/lib.rs
+++ b/cumulus/polkadot-parachains/shell-runtime/src/lib.rs
@@ -85,8 +85,8 @@ const AVERAGE_ON_INITIALIZE_RATIO: Perbill = Perbill::from_percent(10);
 /// We allow `Normal` extrinsics to fill up the block up to 75%, the rest can be used
 /// by  Operational  extrinsics.
 const NORMAL_DISPATCH_RATIO: Perbill = Perbill::from_percent(75);
-/// We allow for 2 seconds of compute with a 6 second average block time.
-const MAXIMUM_BLOCK_WEIGHT: Weight = 2 * WEIGHT_PER_SECOND;
+/// We allow for .5 seconds of compute with a 12 second average block time.
+const MAXIMUM_BLOCK_WEIGHT: Weight = WEIGHT_PER_SECOND / 2;
 
 parameter_types! {
 	pub const BlockHashCount: BlockNumber = 250;
diff --git a/cumulus/test/runtime/src/lib.rs b/cumulus/test/runtime/src/lib.rs
index 75d65d2e81653362826a5c0689434eeb6fc2fe1f..6bebd8af8f9bfda0a58dbacfa3364ac3ee3bf675 100644
--- a/cumulus/test/runtime/src/lib.rs
+++ b/cumulus/test/runtime/src/lib.rs
@@ -96,7 +96,7 @@ pub const VERSION: RuntimeVersion = RuntimeVersion {
 	transaction_version: 1,
 };
 
-pub const MILLISECS_PER_BLOCK: u64 = 6000;
+pub const MILLISECS_PER_BLOCK: u64 = 12000;
 
 pub const SLOT_DURATION: u64 = MILLISECS_PER_BLOCK;
 
@@ -125,8 +125,8 @@ const AVERAGE_ON_INITIALIZE_RATIO: Perbill = Perbill::from_percent(10);
 /// We allow `Normal` extrinsics to fill up the block up to 75%, the rest can be used
 /// by  Operational  extrinsics.
 const NORMAL_DISPATCH_RATIO: Perbill = Perbill::from_percent(75);
-/// We allow for 2 seconds of compute with a 6 second average block time.
-const MAXIMUM_BLOCK_WEIGHT: Weight = 2 * WEIGHT_PER_SECOND;
+/// We allow for .5 seconds of compute with a 12 second average block time.
+const MAXIMUM_BLOCK_WEIGHT: Weight = WEIGHT_PER_SECOND / 2;
 
 parameter_types! {
 	pub const BlockHashCount: BlockNumber = 250;