diff --git a/NEWS.md b/NEWS.md
index ae1f072c5..2e92c8cf7 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 ## Bugfixes
 
+* `path_tidy()` now always includes a trailing slash for the windows root
+  directory, e.g. `C:/` (#124).
+
 * `path_ext()`, `path_ext_set()` and `path_ext_remove()` now handle paths with
   non-ASCII characters (#120).
 
diff --git a/src/utils.cc b/src/utils.cc
index cfd489719..3d649aeb3 100644
--- a/src/utils.cc
+++ b/src/utils.cc
@@ -45,7 +45,17 @@ get_dirent_type(const char* path, const uv_dirent_type_t& entry_type) {
   return entry_type;
 }
 
-std::string path_tidy_(const std::string in) {
+bool is_windows_path(const std::string& x) {
+  if (x.length() < 2) {
+    return false;
+  }
+  char first = x.at(0);
+
+  return ((first >= 'A' && first <= 'Z') || (first >= 'a' && first <= 'z')) &&
+         x.at(1) == ':';
+}
+
+std::string path_tidy_(const std::string& in) {
   std::string out;
   out.reserve(in.size());
   char prev = '\0';
@@ -75,6 +85,16 @@ std::string path_tidy_(const std::string in) {
     out.push_back(prev);
   }
 
+  if (is_windows_path(out)) {
+    // Append a / if this is a root path
+    if (out.length() == 2) {
+      out.push_back('/');
+    } else if (out.length() > 3 && *out.rbegin() == '/') {
+      out.erase(out.end() - 1);
+    }
+    return out;
+  }
+
   // Remove trailing / from paths (that aren't also the beginning)
   if (out.length() > 1 && *out.rbegin() == '/') {
     out.erase(out.end() - 1);
diff --git a/src/utils.h b/src/utils.h
index ae05faf1f..58edd5728 100644
--- a/src/utils.h
+++ b/src/utils.h
@@ -1,7 +1,7 @@
 #include "Rcpp.h"
 #include "uv.h"
 
-inline Rcpp::CharacterVector asCharacterVector(std::string x) {
+inline Rcpp::CharacterVector asCharacterVector(const std::string& x) {
   return Rcpp::CharacterVector(Rf_mkCharCE(x.c_str(), CE_UTF8));
 }
 
@@ -10,4 +10,4 @@ inline Rcpp::CharacterVector asCharacterVector(std::string x) {
 uv_dirent_type_t get_dirent_type(
     const char* path, const uv_dirent_type_t& entry_type = UV_DIRENT_UNKNOWN);
 
-std::string path_tidy_(const std::string in);
+std::string path_tidy_(const std::string& in);
diff --git a/tests/testthat/test-path.R b/tests/testthat/test-path.R
index b12176a92..47cf8fe7d 100644
--- a/tests/testthat/test-path.R
+++ b/tests/testthat/test-path.R
@@ -105,6 +105,17 @@ describe("path_tidy", {
     expect_equal(path_tidy("foo\\\\bar\\\\baz\\\\"), "foo/bar/baz")
   })
 
+  it("always appends windows root paths with /", {
+    expect_equal(path_tidy("C:"), "C:/")
+    expect_equal(path_tidy("c:"), "c:/")
+    expect_equal(path_tidy("X:"), "X:/")
+    expect_equal(path_tidy("x:"), "x:/")
+    expect_equal(path_tidy("c:/"), "c:/")
+    expect_equal(path_tidy("c://"), "c:/")
+    expect_equal(path_tidy("c:\\"), "c:/")
+    expect_equal(path_tidy("c:\\\\"), "c:/")
+  })
+
   it("passes NA along", {
     expect_equal(path_tidy(NA_character_), NA_character_)
     expect_equal(path_tidy(c("foo/bar", NA_character_)), c("foo/bar", NA_character_))
@@ -238,9 +249,9 @@ describe("path_norm", {
     expect_equal(path_norm("."), ".")
     expect_equal(path_norm(""), ".")
     expect_equal(path_norm("/"), "/")
-    expect_equal(path_norm("c:/"), "c:")
+    expect_equal(path_norm("c:/"), "c:/")
     expect_equal(path_norm("/../.././.."), "/")
-    expect_equal(path_norm("c:/../../.."), "c:")
+    expect_equal(path_norm("c:/../../.."), "c:/")
     expect_equal(path_norm("../.././.."), "../../..")
     expect_equal(path_norm("C:////a/b"), "C:/a/b")
     expect_equal(path_norm("//machine/share//a/b"), "//machine/share/a/b")