diff --git a/polkadot/parachain/src/wasm.rs b/polkadot/parachain/src/wasm.rs
index 61b826e47cca6..92968564b3b98 100644
--- a/polkadot/parachain/src/wasm.rs
+++ b/polkadot/parachain/src/wasm.rs
@@ -61,7 +61,7 @@ impl ModuleImportResolver for Resolver {
 		descriptor: &MemoryDescriptor,
 	) -> Result<MemoryRef, WasmError> {
 		if field_name == "memory" {
-			let effective_max = descriptor.maximum().unwrap_or(self.max_memory + 1);
+			let effective_max = descriptor.maximum().unwrap_or(self.max_memory);
 			if descriptor.initial() > self.max_memory || effective_max > self.max_memory {
 				Err(WasmError::Instantiation("Module requested too much memory".to_owned()))
 			} else {
diff --git a/polkadot/parachain/test-chains/basic_add/src/wasm.rs b/polkadot/parachain/test-chains/basic_add/src/wasm.rs
index 95276d3950cbe..e236e22048a7b 100644
--- a/polkadot/parachain/test-chains/basic_add/src/wasm.rs
+++ b/polkadot/parachain/test-chains/basic_add/src/wasm.rs
@@ -22,10 +22,11 @@ use super::{HeadData, BlockData};
 
 #[lang = "panic_fmt"]
 #[no_mangle]
-pub extern "C" fn panic_fmt(
+pub extern fn panic_fmt(
     _args: ::core::fmt::Arguments,
     _file: &'static str,
-    _line: u32
+    _line: u32,
+    _col: u32,
 ) -> ! {
     use core::intrinsics;
     unsafe {
diff --git a/polkadot/parachain/test-chains/build_test_chains.sh b/polkadot/parachain/test-chains/build_test_chains.sh
index d019ffe764948..54c5c9a289603 100755
--- a/polkadot/parachain/test-chains/build_test_chains.sh
+++ b/polkadot/parachain/test-chains/build_test_chains.sh
@@ -6,8 +6,7 @@ for i in */
 do
   i=${i%/}
   cd $i
-  cargo build --target=wasm32-unknown-unknown --release --no-default-features
-  wasm-build --target wasm32-unknown-unknown ./target $i
-  mv ./target/$i.wasm ../../tests/res/$i.wasm
+  RUSTFLAGS="-C link-arg=--import-memory" cargo +nightly-2018-03-07 build --target=wasm32-unknown-unknown --release --no-default-features
+  wasm-gc target/wasm32-unknown-unknown/release/$i.wasm ../../tests/res/$i.wasm
   cd ..
 done
diff --git a/polkadot/parachain/tests/res/basic_add.wasm b/polkadot/parachain/tests/res/basic_add.wasm
index 47dfd0124a4aa..1cd8ab6d19893 100755
Binary files a/polkadot/parachain/tests/res/basic_add.wasm and b/polkadot/parachain/tests/res/basic_add.wasm differ