diff --git a/sim/Cargo.lock b/sim/Cargo.lock
index d34e1c2..0cf7e12 100644
--- a/sim/Cargo.lock
+++ b/sim/Cargo.lock
@@ -194,6 +194,16 @@
 ]
 
 [[package]]
+name = "getrandom"
+version = "0.1.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "cfg-if 0.1.10 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "wasi 0.9.0+wasi-snapshot-preview1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "heck"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -283,6 +293,11 @@
 ]
 
 [[package]]
+name = "ppv-lite86"
+version = "0.2.8"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "proc-macro2"
 version = "1.0.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -316,6 +331,27 @@
 ]
 
 [[package]]
+name = "rand"
+version = "0.7.3"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
+ "libc 0.2.66 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_chacha"
+version = "0.2.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ppv-lite86 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "rand_core"
 version = "0.3.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -329,6 +365,22 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "rand_core"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
+name = "rand_hc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
+[[package]]
 name = "rdrand"
 version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -396,7 +448,7 @@
  "failure 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "failure_derive 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -485,6 +537,11 @@
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
+name = "wasi"
+version = "0.9.0+wasi-snapshot-preview1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
+[[package]]
 name = "wasm-bindgen"
 version = "0.2.58"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -617,6 +674,7 @@
 "checksum failure_derive 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0bc225b78e0391e4b8683440bf2e63c2deeeb2ce5189eab46e2b68c6d3725d08"
 "checksum fuchsia-cprng 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "a06f77d526c1a601b7c4cdd98f54b5eaabffc14d5f2f0296febdc7f357c6d3ba"
 "checksum generic-array 0.12.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c68f0274ae0e023facc3c97b2e00f076be70e254bc851d972503b328db79b2ec"
+"checksum getrandom 0.1.14 (registry+https://github.com/rust-lang/crates.io-index)" = "7abc8dd8451921606d809ba32e95b6111925cd2906060d2dcc29c070220503eb"
 "checksum heck 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "20564e78d53d2bb135c343b3f47714a56af2061f1c928fdb541dc7b9fdd94205"
 "checksum hermit-abi 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "eff2656d88f158ce120947499e971d743c05dbcbed62e5bd2f38f1698bbc3772"
 "checksum humantime 1.3.0 (registry+https://github.com/rust-lang/crates.io-index)" = "df004cfca50ef23c36850aaaa59ad52cc70d0e90243c3c7737a4dd32dc7a3c4f"
@@ -628,12 +686,17 @@
 "checksum nom 4.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2ad2a91a8e869eeb30b9cb3119ae87773a8f4ae617f41b1eb9c154b2905f7bd6"
 "checksum opaque-debug 0.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "2839e79665f131bdb5782e51f2c6c9599c133c6098982a54c794358bf432529c"
 "checksum pem 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "a1581760c757a756a41f0ee3ff01256227bdf64cb752839779b95ffb01c59793"
+"checksum ppv-lite86 0.2.8 (registry+https://github.com/rust-lang/crates.io-index)" = "237a5ed80e274dbc66f86bd59c1e25edc039660be53194b5fe0a482e0f2612ea"
 "checksum proc-macro2 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)" = "3acb317c6ff86a4e579dfa00fc5e6cca91ecbb4e7eb2df0468805b674eb88548"
 "checksum quick-error 1.2.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a1d01941d82fa2ab50be1e79e6714289dd7cde78eba4c074bc5a4374f650dfe0"
 "checksum quote 1.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "053a8c8bcc71fcce321828dc897a98ab9760bef03a4fc36693c231e5b3216cfe"
 "checksum rand 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)" = "552840b97013b1a26992c11eac34bdd778e464601a4c2054b5f0bff7c6761293"
+"checksum rand 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)" = "6a6b1679d49b24bbfe0c803429aa1874472f50d9b363131f0e89fc356b544d03"
+"checksum rand_chacha 0.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "f4c8ed856279c9737206bf725bf36935d8666ead7aa69b52be55af369d193402"
 "checksum rand_core 0.3.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7a6fdeb83b075e8266dcc8762c22776f6877a63111121f5f8c7411e5be7eed4b"
 "checksum rand_core 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "9c33a3c44ca05fa6f1807d8e6743f3824e8509beca625669633be0acbdf509dc"
+"checksum rand_core 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "90bde5296fc891b0cef12a6d03ddccc162ce7b2aff54160af9338f8d40df6d19"
+"checksum rand_hc 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "ca3129af7b92a17112d59ad498c6f81eaf463253766b90396d39ea7a39d6613c"
 "checksum rdrand 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "678054eb77286b51581ba43620cc911abf02758c91f93f479767aed0f90458b2"
 "checksum regex 1.3.4 (registry+https://github.com/rust-lang/crates.io-index)" = "322cf97724bea3ee221b78fe25ac9c46114ebb51747ad5babd51a2fc6a8235a8"
 "checksum regex-syntax 0.6.14 (registry+https://github.com/rust-lang/crates.io-index)" = "b28dfe3fe9badec5dbf0a79a9cccad2cfc2ab5484bdb3e44cbd1ae8b3ba2be06"
@@ -654,6 +717,7 @@
 "checksum unicode-xid 0.2.0 (registry+https://github.com/rust-lang/crates.io-index)" = "826e7639553986605ec5979c7dd957c7895e93eabed50ab2ffa7f6128a75097c"
 "checksum untrusted 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "60369ef7a31de49bcb3f6ca728d4ba7300d9a1658f94c727d4cab8c8d9f4aece"
 "checksum version_check 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)" = "914b1a6776c4c929a602fafd8bc742e06365d4bcbe48c30f9cca5824f70dc9dd"
+"checksum wasi 0.9.0+wasi-snapshot-preview1 (registry+https://github.com/rust-lang/crates.io-index)" = "cccddf32554fecc6acb585f82a32a72e28b48f8c4c1883ddfeeeaa96f7d8e519"
 "checksum wasm-bindgen 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)" = "5205e9afdf42282b192e2310a5b463a6d1c1d774e30dc3c791ac37ab42d2616c"
 "checksum wasm-bindgen-backend 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)" = "11cdb95816290b525b32587d76419facd99662a07e59d3cdb560488a819d9a45"
 "checksum wasm-bindgen-macro 0.2.58 (registry+https://github.com/rust-lang/crates.io-index)" = "574094772ce6921576fb6f2e3f7497b8a76273b6db092be18fc48a082de09dc3"
diff --git a/sim/simflash/Cargo.toml b/sim/simflash/Cargo.toml
index 36776e4..1622255 100644
--- a/sim/simflash/Cargo.toml
+++ b/sim/simflash/Cargo.toml
@@ -7,5 +7,5 @@
 [dependencies]
 failure = "0.1.6"
 failure_derive = "0.1.6"
-rand = "0.4"
+rand = "0.7"
 log = "0.4"
diff --git a/sim/simflash/src/lib.rs b/sim/simflash/src/lib.rs
index c991d47..734b3c1 100644
--- a/sim/simflash/src/lib.rs
+++ b/sim/simflash/src/lib.rs
@@ -15,7 +15,8 @@
 use log::info;
 use rand::{
     self,
-    distributions::{IndependentSample, Range},
+    distributions::Standard,
+    Rng,
 };
 use std::{
     collections::HashMap,
@@ -188,8 +189,8 @@
         for &(off, len, rate) in &self.bad_region {
             if offset >= off && (offset + payload.len()) <= (off + len) {
                 let mut rng = rand::thread_rng();
-                let between = Range::new(0., 1.);
-                if between.ind_sample(&mut rng) < rate {
+                let samp: f32 = rng.sample(Standard);
+                if samp < rate {
                     bail!(esimulatedwrite(
                         format!("Ignoring write to {:#x}-{:#x}", off, off + len)));
                 }