diff --git a/atomics-contract/src/main.rs b/atomics-contract/src/main.rs
index 92b99e2..c76b04b 100644
--- a/atomics-contract/src/main.rs
+++ b/atomics-contract/src/main.rs
@@ -4,12 +4,15 @@
 #[cfg(test)]
 extern crate alloc;
 
-#[cfg(not(test))]
-use ckb_std::default_alloc;
 #[cfg(not(test))]
 ckb_std::entry!(program_entry);
-#[cfg(not(test))]
-default_alloc!();
+// By default, the following heap configuration is used:
+// * 16KB fixed heap
+// * 1.2MB(rounded up to be 16-byte aligned) dynamic heap
+// * Minimal memory block in dynamic heap is 64 bytes
+// For more details, please refer to ckb-std's default_alloc macro
+// and the buddy-alloc alloc implementation.
+ckb_std::default_alloc!(16384, 1258306, 64);
 
 pub fn program_entry() -> i8 {
     log::error!("Just a log line");
diff --git a/contract/src/main.rs b/contract/src/main.rs
index dedabe3..db5049e 100644
--- a/contract/src/main.rs
+++ b/contract/src/main.rs
@@ -7,7 +7,13 @@ extern crate alloc;
 #[cfg(not(any(feature = "native-simulator", test)))]
 ckb_std::entry!(program_entry);
 #[cfg(not(any(feature = "native-simulator", test)))]
-ckb_std::default_alloc!();
+// By default, the following heap configuration is used:
+// * 16KB fixed heap
+// * 1.2MB(rounded up to be 16-byte aligned) dynamic heap
+// * Minimal memory block in dynamic heap is 64 bytes
+// For more details, please refer to ckb-std's default_alloc macro
+// and the buddy-alloc alloc implementation.
+ckb_std::default_alloc!(16384, 1258306, 64);
 
 pub fn program_entry() -> i8 {
     ckb_std::debug!("This is a sample contract!");
diff --git a/stack-reorder-contract/src/main.rs b/stack-reorder-contract/src/main.rs
index 93a65a6..e9e6798 100644
--- a/stack-reorder-contract/src/main.rs
+++ b/stack-reorder-contract/src/main.rs
@@ -4,12 +4,15 @@
 #[cfg(test)]
 extern crate alloc;
 
-#[cfg(not(test))]
-use ckb_std::default_alloc;
 #[cfg(not(test))]
 ckb_std::entry!(program_entry);
-#[cfg(not(test))]
-default_alloc!();
+// By default, the following heap configuration is used:
+// * 16KB fixed heap
+// * 1.2MB(rounded up to be 16-byte aligned) dynamic heap
+// * Minimal memory block in dynamic heap is 64 bytes
+// For more details, please refer to ckb-std's default_alloc macro
+// and the buddy-alloc alloc implementation.
+ckb_std::default_alloc!(16384, 1258306, 64);
 
 #[allow(unused_variables, unused_assignments)]
 pub fn program_entry() -> i8 {
diff --git a/standalone-contract/src/main.rs b/standalone-contract/src/main.rs
index bf6e0c7..f6057e1 100644
--- a/standalone-contract/src/main.rs
+++ b/standalone-contract/src/main.rs
@@ -7,12 +7,16 @@ extern crate alloc;
 #[cfg(test)]
 mod tests;
 
-#[cfg(not(test))]
-use ckb_std::default_alloc;
 #[cfg(not(test))]
 ckb_std::entry!(program_entry);
 #[cfg(not(test))]
-default_alloc!();
+// By default, the following heap configuration is used:
+// * 16KB fixed heap
+// * 1.2MB(rounded up to be 16-byte aligned) dynamic heap
+// * Minimal memory block in dynamic heap is 64 bytes
+// For more details, please refer to ckb-std's default_alloc macro
+// and the buddy-alloc alloc implementation.
+ckb_std::default_alloc!(16384, 1258306, 64);
 
 pub fn program_entry() -> i8 {
     ckb_std::debug!("This is a sample contract!");