diff --git a/circle.yml b/circle.yml
index fc01e76..c1c1c1f 100644
--- a/circle.yml
+++ b/circle.yml
@@ -23,4 +23,10 @@ jobs:
           command: cargo test --target=x86_64-unknown-linux-gnu
       - run:
           name: Build
-          command: cargo build --release
+          command: |
+             cargo build --release
+             # debug
+             cargo build
+             cargo build --release --no-default-features
+             cargo build --release --features debug
+             cargo build --release --no-default-features --features debug
diff --git a/src/debug.rs b/src/debug.rs
index 5c20b9f..0678c81 100644
--- a/src/debug.rs
+++ b/src/debug.rs
@@ -1,6 +1,8 @@
 //! The native debug interface exposed to the ewasm contract. These functions are for testing
 //! purposes only. On a live VM, any bytecode trying to import these symbols will be rejected.
 
+use crate::types::*;
+
 mod native {
     extern "C" {
         pub fn debug_print32(value: u32);
@@ -16,16 +18,16 @@ pub fn print32(value: u32) {
     unsafe { native::debug_print32(value) }
 }
 
-pub fn print64(value: u32) {
+pub fn print64(value: u64) {
     unsafe { native::debug_print64(value) }
 }
 
 pub fn printMem(slice: &[u8]) {
-    unsafe { native::debug_printMem(slice.bytes.as_ptr() as *const u32, slice.len()) }
+    unsafe { native::debug_printMem(slice.as_ptr() as *const u32, slice.len() as u32) }
 }
 
 pub fn printMemHex(slice: &[u8]) {
-    unsafe { native::debug_printMem(slice.bytes.as_ptr() as *const u32, slice.len()) }
+    unsafe { native::debug_printMem(slice.as_ptr() as *const u32, slice.len() as u32) }
 }
 
 pub fn printStorage(key: &StorageKey) {