diff --git a/src/database/keyval.rs b/src/database/keyval.rs
index 79f1398f..0f5665eb 100644
--- a/src/database/keyval.rs
+++ b/src/database/keyval.rs
@@ -17,8 +17,8 @@ pub type Buffer<const CAP: usize = DEF_STACK_CAP> = SmallVec<[Byte; CAP]>;
 pub type Slice = [Byte];
 pub type Byte = u8;
 
-pub const KEY_STACK_CAP: usize = 128;
-pub const VAL_STACK_CAP: usize = 512;
+pub const KEY_STACK_CAP: usize = 128 - 16;
+pub const VAL_STACK_CAP: usize = 512 - 16;
 pub const DEF_STACK_CAP: usize = KEY_STACK_CAP;
 
 #[inline]
diff --git a/src/service/sending/mod.rs b/src/service/sending/mod.rs
index 91d4a439..8bb0f659 100644
--- a/src/service/sending/mod.rs
+++ b/src/service/sending/mod.rs
@@ -75,7 +75,7 @@ pub enum SendingEvent {
 pub type EduBuf = SmallVec<[u8; EDU_BUF_CAP]>;
 pub type EduVec = SmallVec<[EduBuf; EDU_VEC_CAP]>;
 
-const EDU_BUF_CAP: usize = 128;
+const EDU_BUF_CAP: usize = 128 - 16;
 const EDU_VEC_CAP: usize = 1;
 
 #[async_trait]