diff --git a/src/clang_complete.cc b/src/clang_complete.cc
index ee8d954b..10bf7d72 100644
--- a/src/clang_complete.cc
+++ b/src/clang_complete.cc
@@ -28,7 +28,7 @@ namespace {
 std::string StripFileType(const std::string &path) {
   SmallString<128> Ret;
   sys::path::append(Ret, sys::path::parent_path(path), sys::path::stem(path));
-  return Ret.str();
+  return sys::path::convert_to_slash(Ret);
 }
 
 bool LocationInRange(SourceLocation L, CharSourceRange R,
diff --git a/src/clang_utils.cc b/src/clang_utils.cc
index 7a5b930a..1026a6f3 100644
--- a/src/clang_utils.cc
+++ b/src/clang_utils.cc
@@ -22,7 +22,7 @@ std::string FileName(const FileEntry &file) {
   if (!StartsWith(ret, g_config->projectRoot)) {
     SmallString<256> dest;
     sys::fs::real_path(ret, dest);
-    ret = dest.str();
+    ret = sys::path::convert_to_slash(dest.str());
   }
   return ret;
 }
diff --git a/src/filesystem.cc b/src/filesystem.cc
index 3e9a2fbb..2507db0c 100644
--- a/src/filesystem.cc
+++ b/src/filesystem.cc
@@ -47,7 +47,7 @@ void GetFilesInFolder(std::string folder, bool recursive, bool dir_prefix,
         if (sys::fs::is_regular_file(Status)) {
           if (!dir_prefix)
             path = path.substr(folder.size());
-          handler(path);
+          handler(sys::path::convert_to_slash(path));
         } else if (recursive && sys::fs::is_directory(Status) &&
                    !seen.count(ID = Status.getUniqueID())) {
           curr.push_back(path);
diff --git a/src/indexer.cc b/src/indexer.cc
index b663cbe1..421d4488 100644
--- a/src/indexer.cc
+++ b/src/indexer.cc
@@ -552,7 +552,7 @@ public:
       if (!llvm::sys::path::is_absolute(Path) &&
           !SM.getFileManager().makeAbsolutePath(Path))
         return -1;
-      it->second.second = Path.str();
+      it->second.second = llvm::sys::path::convert_to_slash(Path.str());
     }
     return it->second.first;
   }
diff --git a/src/lsp.cc b/src/lsp.cc
index 953b1852..b134f477 100644
--- a/src/lsp.cc
+++ b/src/lsp.cc
@@ -8,6 +8,7 @@
 
 #include <rapidjson/writer.h>
 
+#include <algorithm>
 #include <stdio.h>
 
 MessageRegistry *MessageRegistry::instance_ = nullptr;
@@ -208,10 +209,15 @@ void lsDocumentUri::SetPath(const std::string &path) {
 }
 
 std::string lsDocumentUri::GetPath() const {
-  if (raw_uri.compare(0, 8, "file:///"))
+  if (raw_uri.compare(0, 7, "file://")) {
+    LOG_S(WARNING)
+        << "Received potentially bad URI (not starting with file://): "
+        << raw_uri;
     return raw_uri;
+  }
   std::string ret;
 #ifdef _WIN32
+  // Skipping the initial "/" on Windows
   size_t i = 8;
 #else
   size_t i = 7;
@@ -224,8 +230,14 @@ std::string lsDocumentUri::GetPath() const {
       ret.push_back(from_hex(raw_uri[i + 1]) * 16 + from_hex(raw_uri[i + 2]));
       i += 2;
     } else
-      ret.push_back(raw_uri[i] == '\\' ? '/' : raw_uri[i]);
+      ret.push_back(raw_uri[i]);
   }
+#ifdef _WIN32
+  std::replace(ret.begin(), ret.end(), '\\', '/');
+  if (ret.size() > 1 && ret[0] >= 'a' && ret[0] <= 'z' && ret[1] == ':') {
+    ret[0] = toupper(ret[0]);
+  }
+#endif
   return ret;
 }
 
diff --git a/src/platform_win.cc b/src/platform_win.cc
index f4ebf188..36ebc839 100644
--- a/src/platform_win.cc
+++ b/src/platform_win.cc
@@ -23,14 +23,19 @@ std::string NormalizePath(const std::string &path) {
   TCHAR buffer[MAX_PATH] = TEXT("");
   TCHAR **lpp_part = {NULL};
 
+  std::string result;
   retval = GetFullPathName(path.c_str(), MAX_PATH, buffer, lpp_part);
   // fail, return original
   if (retval == 0)
-    return path;
+    result = path;
+  else
+    result = buffer;
 
-  std::string result = buffer;
   std::replace(result.begin(), result.end(), '\\', '/');
-  // std::transform(result.begin(), result.end(), result.begin(), ::tolower);
+  // Normalize drive letter.
+  if (result.size() > 1 && result[0] >= 'a' && result[0] <= 'z' &&
+      result[1] == ':')
+    result[0] = toupper(result[0]);
   return result;
 }
 
diff --git a/src/project.cc b/src/project.cc
index db83659a..a14431be 100644
--- a/src/project.cc
+++ b/src/project.cc
@@ -160,7 +160,8 @@ struct ProjectProcessor {
 
     HeaderSearchOptions &HeaderOpts = CI->getHeaderSearchOpts();
     for (auto &E : HeaderOpts.UserEntries) {
-      std::string path = ResolveIfRelative(entry.directory, E.Path);
+      std::string path =
+          NormalizePath(ResolveIfRelative(entry.directory, E.Path));
       switch (E.Group) {
       default:
         config->angle_dirs.insert(path);
@@ -315,8 +316,9 @@ LoadEntriesFromDirectory(ProjectConfig *project,
   ProjectProcessor proc(project);
   for (tooling::CompileCommand &Cmd : CDB->getAllCompileCommands()) {
     Project::Entry entry;
-    entry.directory = std::move(Cmd.Directory);
-    entry.filename = ResolveIfRelative(entry.directory, Cmd.Filename);
+    entry.directory = NormalizePath(Cmd.Directory);
+    entry.filename =
+        NormalizePath(ResolveIfRelative(entry.directory, Cmd.Filename));
     entry.args = std::move(Cmd.CommandLine);
     proc.Process(entry);
     if (Seen.insert(entry.filename).second)