diff --git a/crates/blockchain/src/lib.rs b/crates/blockchain/src/lib.rs
index 7faa1163..dc4f1268 100644
--- a/crates/blockchain/src/lib.rs
+++ b/crates/blockchain/src/lib.rs
@@ -68,13 +68,13 @@ pub struct BlockChainConfig {
     pub proposer_config: ProposerConfig,
 }
 
-/// Milliseconds per interval (800ms ticks).
-pub const MILLISECONDS_PER_INTERVAL: u64 = 800;
-/// Number of intervals per slot (5 intervals of 800ms = 4 seconds).
-pub const INTERVALS_PER_SLOT: u64 = 5;
-/// Milliseconds in a slot (derived from interval duration and count).
-pub const MILLISECONDS_PER_SLOT: u64 = MILLISECONDS_PER_INTERVAL * INTERVALS_PER_SLOT;
+// The interval grid lives in `ethlambda-types` because `ethlambda-storage` also
+// derives slots from `store.time()` and must not carry a second copy of a
+// consensus-critical constant.
 pub use ethlambda_types::block::MAX_ATTESTATIONS_DATA;
+pub use ethlambda_types::constants::{
+    INTERVALS_PER_SLOT, MILLISECONDS_PER_INTERVAL, MILLISECONDS_PER_SLOT,
+};
 pub use sync_status::SyncStatusController;
 /// Future-slot tolerance for gossip attestations, expressed in intervals.
 ///
diff --git a/crates/common/types/src/constants.rs b/crates/common/types/src/constants.rs
index 3066b344..c3434d9a 100644
--- a/crates/common/types/src/constants.rs
+++ b/crates/common/types/src/constants.rs
@@ -8,3 +8,10 @@
 /// eventually be derived from the fork version and genesis validators root.
 // TODO: derive dynamically once the spec defines fork identification.
 pub const FORK_DIGEST: &str = "12345678";
+
+/// Milliseconds per interval (800ms ticks).
+pub const MILLISECONDS_PER_INTERVAL: u64 = 800;
+/// Number of intervals per slot (5 intervals of 800ms = 4 seconds).
+pub const INTERVALS_PER_SLOT: u64 = 5;
+/// Milliseconds in a slot (derived from interval duration and count).
+pub const MILLISECONDS_PER_SLOT: u64 = MILLISECONDS_PER_INTERVAL * INTERVALS_PER_SLOT;