diff --git a/sim/Cargo.lock b/sim/Cargo.lock
index 75ff4ae..9c43c4b 100644
--- a/sim/Cargo.lock
+++ b/sim/Cargo.lock
@@ -3,9 +3,11 @@
 version = "0.1.0"
 dependencies = [
  "docopt 0.6.86 (registry+https://github.com/rust-lang/crates.io-index)",
+ "env_logger 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "error-chain 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "gcc 0.3.38 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)",
+ "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)",
  "rustc-serialize 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -67,6 +69,15 @@
 ]
 
 [[package]]
+name = "env_logger"
+version = "0.3.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "regex 0.1.80 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "error-chain"
 version = "0.7.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -99,6 +110,11 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "log"
+version = "0.3.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "memchr"
 version = "0.1.11"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -185,11 +201,13 @@
 "checksum cfg-if 0.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "de1e760d7b6535af4241fca8bd8adf68e2e7edacc6b29f5d399050c5e48cf88c"
 "checksum dbghelp-sys 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "97590ba53bcb8ac28279161ca943a924d1fd4a8fb3fa63302591647c4fc5b850"
 "checksum docopt 0.6.86 (registry+https://github.com/rust-lang/crates.io-index)" = "4a7ef30445607f6fc8720f0a0a2c7442284b629cf0d049286860fae23e71c4d9"
+"checksum env_logger 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "15abd780e45b3ea4f76b4e9a26ff4843258dd8a3eed2775a0e7368c2e7936c2f"
 "checksum error-chain 0.7.1 (registry+https://github.com/rust-lang/crates.io-index)" = "1cd681735364a04cd5d69f01a4f6768e70473941f8d86d8c224faf6955a75799"
 "checksum gcc 0.3.38 (registry+https://github.com/rust-lang/crates.io-index)" = "553f11439bdefe755bf366b264820f1da70f3aaf3924e594b886beb9c831bcf5"
 "checksum kernel32-sys 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "7507624b29483431c0ba2d82aece8ca6cdba9382bff4ddd0f7490560c056098d"
 "checksum lazy_static 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "6abe0ee2e758cd6bc8a2cd56726359007748fbf4128da998b65d0b70f881e19b"
 "checksum libc 0.2.17 (registry+https://github.com/rust-lang/crates.io-index)" = "044d1360593a78f5c8e5e710beccdc24ab71d1f01bc19a29bcacdba22e8475d8"
+"checksum log 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "ab83497bf8bf4ed2a74259c1c802351fcd67a65baa86394b6ba73c36f4838054"
 "checksum memchr 0.1.11 (registry+https://github.com/rust-lang/crates.io-index)" = "d8b629fb514376c675b98c1421e80b151d3817ac42d7c667717d282761418d20"
 "checksum rand 0.3.15 (registry+https://github.com/rust-lang/crates.io-index)" = "022e0636ec2519ddae48154b028864bdce4eaf7d35226ab8e65c611be97b189d"
 "checksum regex 0.1.80 (registry+https://github.com/rust-lang/crates.io-index)" = "4fd4ace6a8cf7860714a2c2280d6c1f7e6a413486c13298bbc86fd3da019402f"
diff --git a/sim/Cargo.toml b/sim/Cargo.toml
index 6f685d5..a93f299 100644
--- a/sim/Cargo.toml
+++ b/sim/Cargo.toml
@@ -13,6 +13,8 @@
 error-chain = "0.7.1"
 docopt = "0.6"
 rustc-serialize = "0.3"
+log = "0.3"
+env_logger = "0.3"
 
 [profile.test]
 opt-level = 1
diff --git a/sim/csupport/run.c b/sim/csupport/run.c
index 677f40c..e24531f 100644
--- a/sim/csupport/run.c
+++ b/sim/csupport/run.c
@@ -43,7 +43,7 @@
 	flash_areas = adesc;
 	if (setjmp(boot_jmpbuf) == 0) {
 		res = boot_go(&rsp);
-		printf("boot_go result: %d (0x%08x)\n", res, rsp.br_image_addr);
+		/* printf("boot_go result: %d (0x%08x)\n", res, rsp.br_image_addr); */
 		return res;
 	} else {
 		return -0x13579;
diff --git a/sim/src/main.rs b/sim/src/main.rs
index 6822605..1f17f17 100644
--- a/sim/src/main.rs
+++ b/sim/src/main.rs
@@ -1,3 +1,5 @@
+#[macro_use] extern crate log;
+extern crate env_logger;
 extern crate docopt;
 extern crate libc;
 extern crate rand;
@@ -65,6 +67,8 @@
 }
 
 fn main() {
+    env_logger::init().unwrap();
+
     let args: Args = Docopt::new(USAGE)
         .and_then(|d| d.decode())
         .unwrap_or_else(|e| e.exit());
@@ -117,33 +121,33 @@
     mark_upgrade(&mut flash, 0x060000 - trailer_size as usize);
 
     let (fl2, total_count) = try_upgrade(&flash, &areadesc, None);
-    println!("First boot, count={}", total_count);
+    info!("First boot, count={}", total_count);
     assert!(verify_image(&fl2, 0x020000, &upgrade));
 
     let mut bad = 0;
     // Let's try an image halfway through.
     for i in 1 .. total_count {
-        println!("Try interruption at {}", i);
+        info!("Try interruption at {}", i);
         let (fl3, total_count) = try_upgrade(&flash, &areadesc, Some(i));
-        println!("Second boot, count={}", total_count);
+        info!("Second boot, count={}", total_count);
         if !verify_image(&fl3, 0x020000, &upgrade) {
-            println!("FAIL");
+            warn!("FAIL at step {} of {}", i, total_count);
             bad += 1;
         }
         if !verify_image(&fl3, 0x040000, &primary) {
-            println!("Slot 1 FAIL");
+            warn!("Slot 1 FAIL at step {} of {}", i, total_count);
             bad += 1;
         }
     }
-    println!("{} out of {} failed {:.2}%",
-             bad, total_count,
-             bad as f32 * 100.0 / total_count as f32);
+    error!("{} out of {} failed {:.2}%",
+           bad, total_count,
+           bad as f32 * 100.0 / total_count as f32);
 
-    println!("Try revert");
+    info!("Try revert");
     let fl2 = try_revert(&flash, &areadesc);
     assert!(verify_image(&fl2, 0x020000, &primary));
 
-    println!("Try norevert");
+    info!("Try norevert");
     let fl2 = try_norevert(&flash, &areadesc);
     assert!(verify_image(&fl2, 0x020000, &upgrade));
 
@@ -276,7 +280,7 @@
     if buf != &copy[..] {
         for i in 0 .. buf.len() {
             if buf[i] != copy[i] {
-                println!("First failure at {:#x}", offset + i);
+                info!("First failure at {:#x}", offset + i);
                 break;
             }
         }