diff --git a/Cargo.lock b/Cargo.lock
index e007bc610de..9a41e6534ea 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1090,6 +1090,7 @@ dependencies = [
  "unicode-segmentation",
  "unicode-width",
  "unicode_categories",
+ "winapi",
 ]
 
 [[package]]
diff --git a/rustfmt-core/rustfmt-bin/src/bin/main.rs b/rustfmt-core/rustfmt-bin/src/bin/main.rs
index dbddf4d7f63..4f0f7f3010d 100644
--- a/rustfmt-core/rustfmt-bin/src/bin/main.rs
+++ b/rustfmt-core/rustfmt-bin/src/bin/main.rs
@@ -14,7 +14,7 @@ use structopt::StructOpt;
 use thiserror::Error;
 
 use rustfmt_lib::{
-    load_config, CliOptions, Config, Edition, EmitMode, FileLines, FileName,
+    absolute_path, load_config, CliOptions, Config, Edition, EmitMode, FileLines, FileName,
     FormatReportFormatterBuilder, Input, Session, Verbosity,
 };
 
@@ -252,7 +252,7 @@ enum OptError {
 impl Opt {
     fn canonicalize(&mut self) {
         for f in &mut self.files {
-            if let Ok(canonical_path) = f.canonicalize() {
+            if let Ok(canonical_path) = absolute_path(&f) {
                 *f = canonical_path;
             }
         }
diff --git a/rustfmt-core/rustfmt-bin/src/cargo-fmt/main.rs b/rustfmt-core/rustfmt-bin/src/cargo-fmt/main.rs
index cd510d2bf4f..bb92084ffcd 100644
--- a/rustfmt-core/rustfmt-bin/src/cargo-fmt/main.rs
+++ b/rustfmt-core/rustfmt-bin/src/cargo-fmt/main.rs
@@ -13,6 +13,7 @@ use std::path::{Path, PathBuf};
 use std::process::Command;
 use std::str;
 
+use rustfmt_lib::absolute_path;
 use structopt::StructOpt;
 
 #[derive(StructOpt, Debug)]
@@ -288,7 +289,7 @@ impl Target {
         nested_int_test_files: Option<Vec<PathBuf>>,
     ) -> Self {
         let path = PathBuf::from(&target.src_path);
-        let canonicalized = fs::canonicalize(&path).unwrap_or(path);
+        let canonicalized = absolute_path(&path).unwrap_or(path);
         let test_files = nested_int_test_files.unwrap_or_else(Vec::new);
 
         Self {
@@ -388,14 +389,14 @@ fn get_targets_root_only(
     include_nested_test_files: bool,
 ) -> Result<(), io::Error> {
     let metadata = get_cargo_metadata(manifest_path, false)?;
-    let workspace_root_path = PathBuf::from(&metadata.workspace_root).canonicalize()?;
+    let workspace_root_path = absolute_path(PathBuf::from(&metadata.workspace_root))?;
     let (in_workspace_root, current_dir_manifest) = if let Some(target_manifest) = manifest_path {
         (
             workspace_root_path == target_manifest,
-            target_manifest.canonicalize()?,
+            absolute_path(target_manifest)?,
         )
     } else {
-        let current_dir = env::current_dir()?.canonicalize()?;
+        let current_dir = absolute_path(env::current_dir()?)?;
         (
             workspace_root_path == current_dir,
             current_dir.join("Cargo.toml"),
@@ -413,9 +414,7 @@ fn get_targets_root_only(
                 .into_iter()
                 .filter(|p| {
                     in_workspace_root
-                        || PathBuf::from(&p.manifest_path)
-                            .canonicalize()
-                            .unwrap_or_default()
+                        || absolute_path(PathBuf::from(&p.manifest_path)).unwrap_or_default()
                             == current_dir_manifest
                 })
                 .map(|p| p.targets)
@@ -1052,7 +1051,7 @@ mod cargo_fmt_tests {
             edition: &str,
         ) -> Target {
             let path = PathBuf::from(src_path);
-            let canonicalized = fs::canonicalize(&path).unwrap_or(path);
+            let canonicalized = absolute_path(&path).unwrap_or(path);
             Target {
                 path: canonicalized,
                 kind: String::from(kind),
diff --git a/rustfmt-core/rustfmt-lib/Cargo.toml b/rustfmt-core/rustfmt-lib/Cargo.toml
index 827c3c3f614..ae9a309604d 100644
--- a/rustfmt-core/rustfmt-lib/Cargo.toml
+++ b/rustfmt-core/rustfmt-lib/Cargo.toml
@@ -50,6 +50,9 @@ serde = { version = "1.0", features = ["derive"], optional = true }
 serde_json = { version = "1.0", optional = true }
 toml = { version = "0.5", optional = true }
 
+[target.'cfg(windows)'.dependencies]
+winapi = { version = "0.3", features = ["errhandlingapi", "fileapi"] }
+
 [dev-dependencies]
 env_logger = "0.7"
 
diff --git a/rustfmt-core/rustfmt-lib/src/config.rs b/rustfmt-core/rustfmt-lib/src/config.rs
index 17c654a7ecf..decc9be25a1 100644
--- a/rustfmt-core/rustfmt-lib/src/config.rs
+++ b/rustfmt-core/rustfmt-lib/src/config.rs
@@ -8,11 +8,13 @@ use std::{env, fs};
 use regex::Regex;
 use thiserror::Error;
 
-use crate::config::config_type::ConfigType;
 pub use crate::config::file_lines::{FileLines, FileName, Range};
 pub use crate::config::lists::*;
 pub use crate::config::options::*;
 
+use crate::config::config_type::ConfigType;
+use crate::utils::absolute_path;
+
 #[macro_use]
 pub mod config_type;
 #[macro_use]
@@ -236,7 +238,7 @@ impl Config {
                 dir.to_path_buf()
             };
 
-            current = fs::canonicalize(current)?;
+            current = absolute_path(current)?;
 
             loop {
                 match get_toml_path(&current) {
diff --git a/rustfmt-core/rustfmt-lib/src/config/file_lines.rs b/rustfmt-core/rustfmt-lib/src/config/file_lines.rs
index 64b2a8dc866..946f5bd2b67 100644
--- a/rustfmt-core/rustfmt-lib/src/config/file_lines.rs
+++ b/rustfmt-core/rustfmt-lib/src/config/file_lines.rs
@@ -12,6 +12,8 @@ use thiserror::Error;
 
 use rustc_span::{self, SourceFile};
 
+use crate::utils::absolute_path;
+
 /// A range of lines in a file, inclusive of both ends.
 pub struct LineRange {
     pub file: Rc<SourceFile>,
@@ -295,7 +297,7 @@ impl<'a> iter::Iterator for Files<'a> {
 
 fn canonicalize_path_string(file: &FileName) -> std::io::Result<FileName> {
     match *file {
-        FileName::Real(ref path) => path.canonicalize().map(FileName::Real),
+        FileName::Real(ref path) => absolute_path(path).map(FileName::Real),
         _ => Ok(file.clone()),
     }
 }
diff --git a/rustfmt-core/rustfmt-lib/src/lib.rs b/rustfmt-core/rustfmt-lib/src/lib.rs
index 7c485b51a63..919243fd6ce 100644
--- a/rustfmt-core/rustfmt-lib/src/lib.rs
+++ b/rustfmt-core/rustfmt-lib/src/lib.rs
@@ -18,21 +18,20 @@ use std::rc::Rc;
 use rustc_ast::ast;
 use thiserror::Error;
 
-use crate::comment::LineClasses;
-use crate::formatting::{FormatErrorMap, FormattingError, ReportedErrors, SourceFile};
-use crate::shape::Indent;
-use crate::syntux::parser::DirectoryOwnership;
-use crate::utils::indent_next_line;
-
 pub use crate::config::{
     load_config, CliOptions, Color, Config, Edition, EmitMode, FileLines, FileName, NewlineStyle,
     Range, Verbosity,
 };
-
+pub use crate::emitter::rustfmt_diff::{ModifiedChunk, ModifiedLines};
 pub use crate::format_report_formatter::{FormatReportFormatter, FormatReportFormatterBuilder};
+pub use crate::utils::absolute_path;
 
-pub use crate::emitter::rustfmt_diff::{ModifiedChunk, ModifiedLines};
+use crate::comment::LineClasses;
 use crate::emitter::Emitter;
+use crate::formatting::{FormatErrorMap, FormattingError, ReportedErrors, SourceFile};
+use crate::shape::Indent;
+use crate::syntux::parser::DirectoryOwnership;
+use crate::utils::indent_next_line;
 
 #[macro_use]
 mod utils;
diff --git a/rustfmt-core/rustfmt-lib/src/test/mod.rs b/rustfmt-core/rustfmt-lib/src/test/mod.rs
index 75a8d1c8ba1..c7de8ab068e 100644
--- a/rustfmt-core/rustfmt-lib/src/test/mod.rs
+++ b/rustfmt-core/rustfmt-lib/src/test/mod.rs
@@ -40,6 +40,7 @@ const SKIP_FILE_WHITE_LIST: &[&str] = &[
     // these files directly
     "configs/recursive/disabled/foo.rs",
     "configs/recursive/enabled/foo.rs",
+    "mods-relative-path/mod_b.rs",
 ];
 
 fn init_log() {
diff --git a/rustfmt-core/rustfmt-lib/src/utils.rs b/rustfmt-core/rustfmt-lib/src/utils.rs
index 63b09537961..61b85d88db0 100644
--- a/rustfmt-core/rustfmt-lib/src/utils.rs
+++ b/rustfmt-core/rustfmt-lib/src/utils.rs
@@ -1,4 +1,6 @@
 use std::borrow::Cow;
+use std::io;
+use std::path;
 
 use rustc_ast::ast::{
     self, Attribute, CrateSugar, MetaItem, MetaItemKind, NestedMetaItem, NodeId, Path, Visibility,
@@ -661,6 +663,47 @@ pub(crate) fn unicode_str_width(s: &str) -> usize {
     s.width()
 }
 
+#[cfg(windows)]
+pub fn absolute_path<P: AsRef<path::Path>>(p: P) -> io::Result<path::PathBuf> {
+    use std::ffi::OsString;
+    use std::iter::once;
+    use std::os::windows::ffi::{OsStrExt, OsStringExt};
+    use std::ptr::null_mut;
+    use winapi::um::errhandlingapi::GetLastError;
+    use winapi::um::fileapi::GetFullPathNameW;
+
+    // FIXME: This `MAX_PATH` may be valid only from Windows 10, version 1607.
+    // https://docs.microsoft.com/ja-jp/windows/desktop/FileIO/naming-a-file#paths
+    const MAX_PATH: usize = 32767;
+    let wide: Vec<u16> = p
+        .as_ref()
+        .as_os_str()
+        .encode_wide()
+        .chain(once(0))
+        .collect();
+    let mut buffer: Vec<u16> = vec![0; MAX_PATH];
+    unsafe {
+        let result = GetFullPathNameW(
+            wide.as_ptr(),
+            MAX_PATH as u32,
+            buffer.as_mut_ptr(),
+            null_mut(),
+        );
+        if result == 0 {
+            Err(io::Error::from_raw_os_error(GetLastError() as i32))
+        } else {
+            Ok(path::PathBuf::from(OsString::from_wide(
+                &buffer[..result as usize],
+            )))
+        }
+    }
+}
+
+#[cfg(not(windows))]
+pub fn absolute_path<P: AsRef<path::Path>>(p: P) -> io::Result<path::PathBuf> {
+    std::fs::canonicalize(p)
+}
+
 #[cfg(test)]
 mod test {
     use super::*;
diff --git a/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/lib.rs b/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/lib.rs
new file mode 100644
index 00000000000..4c56a8b1ded
--- /dev/null
+++ b/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/lib.rs
@@ -0,0 +1,4 @@
+// rustfmt-recursive: true
+
+#[path = "../mods-relative-paths/mod_b.rs"]
+mod b;
diff --git a/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/mod_b.rs b/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/mod_b.rs
new file mode 100644
index 00000000000..85f9f3f0a4f
--- /dev/null
+++ b/rustfmt-core/rustfmt-lib/tests/source/mods-relative-paths/mod_b.rs
@@ -0,0 +1,7 @@
+fn
+
+
+
+foo() {
+               println!("toto")
+}
diff --git a/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/lib.rs b/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/lib.rs
new file mode 100644
index 00000000000..4c56a8b1ded
--- /dev/null
+++ b/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/lib.rs
@@ -0,0 +1,4 @@
+// rustfmt-recursive: true
+
+#[path = "../mods-relative-paths/mod_b.rs"]
+mod b;
diff --git a/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/mod_b.rs b/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/mod_b.rs
new file mode 100644
index 00000000000..3b0991e5071
--- /dev/null
+++ b/rustfmt-core/rustfmt-lib/tests/target/mods-relative-paths/mod_b.rs
@@ -0,0 +1,3 @@
+fn foo() {
+    println!("toto")
+}