diff --git a/Cargo.lock b/Cargo.lock
index 1f11176..319aea0 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -3,7 +3,7 @@ name = "aho-corasick"
 version = "0.6.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "memchr 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -112,7 +112,7 @@ version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)",
- "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "time 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
@@ -155,8 +155,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "strum 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "strum_macros 0.9.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -171,7 +171,7 @@ dependencies = [
  "humantime 1.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "termcolor 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "termcolor 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -257,7 +257,7 @@ dependencies = [
  "pest_derive 1.0.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "quick-error 1.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "walkdir 2.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -454,8 +454,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "phf 0.7.23 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf_codegen 0.7.23 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache 0.7.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache_codegen 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -469,8 +469,8 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "mdbook"
-version = "0.2.1"
-source = "registry+https://github.com/rust-lang/crates.io-index"
+version = "0.2.2-alpha.0"
+source = "git+https://github.com/rust-lang-nursery/mdBook#df874cdbdb095234703ef9eb267060e2f8463048"
 dependencies = [
  "ammonia 1.2.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "chrono 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -483,17 +483,17 @@ dependencies = [
  "itertools 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
  "lazy_static 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "notify 4.0.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "open 1.2.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "pulldown-cmark 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex 1.0.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde_derive 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_derive 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_json 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)",
  "shlex 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "staticfile 0.5.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "tempfile 3.0.3 (registry+https://github.com/rust-lang/crates.io-index)",
+ "tempfile 3.0.4 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml 0.4.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "toml-query 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "ws 0.7.8 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -506,17 +506,19 @@ dependencies = [
  "clap 2.32.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "env_logger 0.5.13 (registry+https://github.com/rust-lang/crates.io-index)",
  "log 0.4.5 (registry+https://github.com/rust-lang/crates.io-index)",
- "mdbook 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "mdbook 0.2.2-alpha.0 (git+https://github.com/rust-lang-nursery/mdBook)",
  "pulldown-cmark 0.1.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "pulldown-cmark-to-cmark 1.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "memchr"
-version = "2.0.2"
+version = "2.1.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
+ "version_check 0.1.4 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -633,12 +635,12 @@ name = "num-integer"
 version = "0.1.39"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)",
+ "num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
 name = "num-traits"
-version = "0.2.5"
+version = "0.2.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
@@ -859,7 +861,7 @@ version = "1.0.5"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "aho-corasick 0.6.8 (registry+https://github.com/rust-lang/crates.io-index)",
- "memchr 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)",
+ "memchr 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)",
  "regex-syntax 0.6.2 (registry+https://github.com/rust-lang/crates.io-index)",
  "thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "utf8-ranges 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -937,12 +939,12 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "serde"
-version = "1.0.78"
+version = "1.0.79"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
 [[package]]
 name = "serde_derive"
-version = "1.0.78"
+version = "1.0.79"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "proc-macro2 0.4.19 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -957,7 +959,7 @@ source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "itoa 0.4.3 (registry+https://github.com/rust-lang/crates.io-index)",
  "ryu 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1013,7 +1015,7 @@ dependencies = [
  "new_debug_unreachable 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "phf_shared 0.7.23 (registry+https://github.com/rust-lang/crates.io-index)",
  "precomputed-hash 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache_codegen 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "string_cache_shared 0.3.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
@@ -1105,9 +1107,10 @@ dependencies = [
 
 [[package]]
 name = "tempfile"
-version = "3.0.3"
+version = "3.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
+ "cfg-if 0.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.43 (registry+https://github.com/rust-lang/crates.io-index)",
  "rand 0.5.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "redox_syscall 0.1.40 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1127,7 +1130,7 @@ dependencies = [
 
 [[package]]
 name = "termcolor"
-version = "1.0.3"
+version = "1.0.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
  "wincolor 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1209,7 +1212,7 @@ name = "toml"
 version = "0.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 dependencies = [
- "serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -1472,8 +1475,8 @@ dependencies = [
 "checksum maplit 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "08cbb6b4fef96b6d77bfc40ec491b1690c779e77b05cd9f07f787ed376fd4c43"
 "checksum markup5ever 0.7.2 (registry+https://github.com/rust-lang/crates.io-index)" = "bfedc97d5a503e96816d10fedcd5b42f760b2e525ce2f7ec71f6a41780548475"
 "checksum matches 0.1.8 (registry+https://github.com/rust-lang/crates.io-index)" = "7ffc5c5338469d4d3ea17d269fa8ea3512ad247247c30bd2df69e68309ed0a08"
-"checksum mdbook 0.2.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a137498976d9c7a6a07bd31c132bf6c3477d824e585436f5ccf47ab538d738c"
-"checksum memchr 2.0.2 (registry+https://github.com/rust-lang/crates.io-index)" = "a3b4142ab8738a78c51896f704f83c11df047ff1bda9a92a661aa6361552d93d"
+"checksum mdbook 0.2.2-alpha.0 (git+https://github.com/rust-lang-nursery/mdBook)" = "<none>"
+"checksum memchr 2.1.0 (registry+https://github.com/rust-lang/crates.io-index)" = "4b3629fe9fdbff6daa6c33b90f7c08355c1aca05a3d01fa8063b822fcf185f3b"
 "checksum mime 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "ba626b8a6de5da682e1caa06bdb42a335aee5a84db8e5046a3e8ab17ba0a3ae0"
 "checksum mime_guess 1.8.6 (registry+https://github.com/rust-lang/crates.io-index)" = "2d4c0961143b8efdcfa29c3ae63281601b446a4a668165454b6c90f8024954c5"
 "checksum mio 0.6.16 (registry+https://github.com/rust-lang/crates.io-index)" = "71646331f2619b1026cc302f87a2b8b648d5c6dd6937846a16cc8ce0f347f432"
@@ -1485,7 +1488,7 @@ dependencies = [
 "checksum new_debug_unreachable 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "0cdc457076c78ab54d5e0d6fa7c47981757f1e34dc39ff92787f217dede586c4"
 "checksum notify 4.0.6 (registry+https://github.com/rust-lang/crates.io-index)" = "873ecfd8c174964ae30f401329d140142312c8e5590719cf1199d5f1717d8078"
 "checksum num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)" = "e83d528d2677f0518c570baf2b7abdcf0cd2d248860b68507bdcb3e91d4c0cea"
-"checksum num-traits 0.2.5 (registry+https://github.com/rust-lang/crates.io-index)" = "630de1ef5cc79d0cdd78b7e33b81f083cbfe90de0f4b2b2f07f905867c70e9fe"
+"checksum num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0b3a5d7cc97d6d30d8b9bc8fa19bf45349ffe46241e8816f50f62f6d6aaabee1"
 "checksum num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c51a3322e4bca9d212ad9a158a02abc6934d005490c054a2778df73a70aa0a30"
 "checksum open 1.2.2 (registry+https://github.com/rust-lang/crates.io-index)" = "eedfa0ca7b54d84d948bfd058b8f82e767d11f362dd78c36866fd1f69c175867"
 "checksum owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "cdf84f41639e037b484f93433aa3897863b561ed65c6e59c7073d7c561710f37"
@@ -1525,8 +1528,8 @@ dependencies = [
 "checksum semver 0.9.0 (registry+https://github.com/rust-lang/crates.io-index)" = "1d7eb9ef2c18661902cc47e535f9bc51b78acd254da71d375c2f6720d9a40403"
 "checksum semver-parser 0.7.0 (registry+https://github.com/rust-lang/crates.io-index)" = "388a1df253eca08550bef6c72392cfe7c30914bf41df5269b68cbd6ff8f570a3"
 "checksum sequence_trie 0.3.5 (registry+https://github.com/rust-lang/crates.io-index)" = "32157204e5c9d3c04007bd7e56e96e987635ce0e8e23c085b1e403861b76c351"
-"checksum serde 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)" = "92ec94e2754699adddbbc4f555791bd3acc2a2f5574cba16c93a4a9cf4a04415"
-"checksum serde_derive 1.0.78 (registry+https://github.com/rust-lang/crates.io-index)" = "0fb622d85245add5327d4f08b2d24fd51fa5d35fe1bba19ee79a1f211e9ac0ff"
+"checksum serde 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)" = "84257ccd054dc351472528c8587b4de2dbf0dc0fe2e634030c1a90bfdacebaa9"
+"checksum serde_derive 1.0.79 (registry+https://github.com/rust-lang/crates.io-index)" = "31569d901045afbff7a9479f793177fe9259819aff10ab4f89ef69bbc5f567fe"
 "checksum serde_json 1.0.27 (registry+https://github.com/rust-lang/crates.io-index)" = "59790990c5115d16027f00913e2e66de23a51f70422e549d2ad68c8c5f268f1c"
 "checksum sha1 0.6.0 (registry+https://github.com/rust-lang/crates.io-index)" = "2579985fda508104f7587689507983eadd6a6e84dd35d6d115361f530916fa0d"
 "checksum shlex 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)" = "7fdf1b9db47230893d76faad238fd6097fd6d6a9245cd7a4d90dbd639536bbd2"
@@ -1546,9 +1549,9 @@ dependencies = [
 "checksum syn 0.14.9 (registry+https://github.com/rust-lang/crates.io-index)" = "261ae9ecaa397c42b960649561949d69311f08eeaea86a65696e6e46517cf741"
 "checksum syn 0.15.4 (registry+https://github.com/rust-lang/crates.io-index)" = "9056ebe7f2d6a38bc63171816fd1d3430da5a43896de21676dc5c0a4b8274a11"
 "checksum synom 0.11.3 (registry+https://github.com/rust-lang/crates.io-index)" = "a393066ed9010ebaed60b9eafa373d4b1baac186dd7e008555b0f702b51945b6"
-"checksum tempfile 3.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "c4b103c6d08d323b92ff42c8ce62abcd83ca8efa7fd5bf7927efefec75f58c76"
+"checksum tempfile 3.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "55c1195ef8513f3273d55ff59fe5da6940287a0d7a98331254397f464833675b"
 "checksum tendril 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "9de21546595a0873061940d994bbbc5c35f024ae4fd61ec5c5b159115684f508"
-"checksum termcolor 1.0.3 (registry+https://github.com/rust-lang/crates.io-index)" = "ff3bac0e465b59f194e7037ed404b0326e56ff234d767edc4c5cc9cd49e7a2c7"
+"checksum termcolor 1.0.4 (registry+https://github.com/rust-lang/crates.io-index)" = "4096add70612622289f2fdcdbd5086dc81c1e2675e6ae58d6c4f62a16c6d7f2f"
 "checksum termion 1.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "689a3bdfaab439fd92bc87df5c4c78417d3cbe537487274e9b0b2dce76e92096"
 "checksum textwrap 0.10.0 (registry+https://github.com/rust-lang/crates.io-index)" = "307686869c93e71f94da64286f9a9524c0f308a9e1c87a583de8e9c9039ad3f6"
 "checksum thread_local 0.3.6 (registry+https://github.com/rust-lang/crates.io-index)" = "c6b53e329000edc2b34dbe8545fd20e55a333362d0a321909685a19bd28c3f1b"
diff --git a/Cargo.toml b/Cargo.toml
index 0b734a4..5eafc3d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -4,7 +4,7 @@ version = "0.1.0"
 authors = ["Jan-Erik Rediger <janerik@fnordig.de>"]
 
 [dependencies]
-mdbook = "0.2.1"
+mdbook = { git = "https://github.com/rust-lang-nursery/mdBook" }
 pulldown-cmark = "0.1.2"
 pulldown-cmark-to-cmark = "1.1.0"
 env_logger = "0.5.10"
diff --git a/src/lib.rs b/src/lib.rs
index 82345bb..5d1eafc 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -17,19 +17,21 @@ impl Preprocessor for Toc {
         "toc"
     }
 
-    fn run(&self, _ctx: &PreprocessorContext, book: &mut Book) -> Result<()> {
-        let mut res: Option<_> = None;
+    fn run(&self, _ctx: &PreprocessorContext, mut book: Book) -> Result<Book> {
+        let mut res = None;
         book.for_each_mut(|item: &mut BookItem| {
             if let Some(Err(_)) = res {
                 return;
             }
+
             if let BookItem::Chapter(ref mut chapter) = *item {
                 res = Some(Toc::add_toc(chapter).map(|md| {
                     chapter.content = md;
                 }));
             }
         });
-        res.unwrap_or(Ok(()))
+
+        res.unwrap_or(Ok(())).map(|_| book)
     }
 }