diff --git a/README.md b/README.md
index 89fbea3..d022f3a 100644
--- a/README.md
+++ b/README.md
@@ -26,9 +26,16 @@ For development puposes, raw WASM contract can be injected with gas counters (th
 cargo run --release --bin wasm-gas -- <input_binary.wasm> <output_binary.wasm>
 ```
 
-## Allocators substiution (wasm-ext)
+## Externalization (wasm-ext)
 
-Parity WASM runtime provides simple memory allocators, if contract requires. When relied on this allocators, WASM binary size can be greatly reduced. This utility scans for `_malloc`, `_free` invokes inside the WASM binary and substitutes them with invokes of the imported `_malloc`, `_free`. Should be run before `wasm-opt` for better results.
+Parity WASM runtime provides some library functions that can be commonly found in libc. WASM binary size can be reduced and performance may be improved if these functions are used. This utility scans for invocations of the following functions inside the WASM binary:
+- `_malloc`,
+- `_free`,
+- `_memcpy`,
+- `_memset`,
+- `_memmove`
+
+And then substitutes them with invocations of the imported ones. Should be run before `wasm-opt` for better results.
 
 ```
 cargo run --release --bin wasm-ext -- <input_binary.wasm> <output_binary.wasm>
diff --git a/build/src/main.rs b/build/src/main.rs
index a95cefe..3f6adb6 100644
--- a/build/src/main.rs
+++ b/build/src/main.rs
@@ -71,8 +71,8 @@ fn main() {
 		.arg(Arg::with_name("skip_optimization")
 			.help("Skip symbol optimization step producing final wasm")
 			.long("skip-optimization"))
-		.arg(Arg::with_name("skip_alloc")
-			.help("Skip allocator externalizer step producing final wasm")
+		.arg(Arg::with_name("skip_externalize")
+			.help("Skip externalizer step producing final wasm")
 			.long("skip-externalize"))
 		.arg(Arg::with_name("runtime_type")
 			.help("Injects RUNTIME_TYPE global export")
@@ -93,10 +93,10 @@ fn main() {
 
 	let mut module = parity_wasm::deserialize_file(&path).unwrap();
 
-	if !matches.is_present("skip_alloc") {
+	if !matches.is_present("skip_externalize") {
 		module = wasm_utils::externalize(
 			module,
-			vec!["_free", "_malloc"],
+			vec!["_free", "_malloc", "_memcpy", "_memset", "_memmove"],
 		);
 	}
 
diff --git a/ext/src/main.rs b/ext/src/main.rs
index 99c7e22..6904d24 100644
--- a/ext/src/main.rs
+++ b/ext/src/main.rs
@@ -14,8 +14,8 @@ fn main() {
 	}
 
 	let module = wasm_utils::externalize(
-		parity_wasm::deserialize_file(&args[1]).expect("Module to deserialize ok"), 
-		vec!["_free", "_malloc"],
+		parity_wasm::deserialize_file(&args[1]).expect("Module to deserialize ok"),
+		vec!["_free", "_malloc", "_memcpy", "_memset", "_memmove"],
 	);
 
 	parity_wasm::serialize_to_file(&args[2], module).expect("Module to serialize ok");