diff --git a/lldb/source/Host/windows/ProcessLauncherWindows.cpp b/lldb/source/Host/windows/ProcessLauncherWindows.cpp
--- a/lldb/source/Host/windows/ProcessLauncherWindows.cpp
+++ b/lldb/source/Host/windows/ProcessLauncherWindows.cpp
@@ -23,10 +23,8 @@
 namespace {
 void CreateEnvironmentBuffer(const Environment &env,
                              std::vector<char> &buffer) {
-  if (env.size() == 0)
-    return;
-
-  // Environment buffer is a null terminated list of null terminated strings
+  // Environment buffer is a list of null-terminated list of strings. It ends
+  // with a double null.
   for (const auto &KV : env) {
     std::wstring warg;
     if (llvm::ConvertUTF8toWide(Environment::compose(KV), warg)) {
@@ -38,6 +36,12 @@
   // One null wchar_t (to end the block) is two null bytes
   buffer.push_back(0);
   buffer.push_back(0);
+  // If the environment was empty, we must insert an extra byte to ensure a
+  // double null.
+  if (env.empty()) {
+    buffer.push_back(0);
+    buffer.push_back(0);
+  }
 }
 
 bool GetFlattenedWindowsCommandString(Args args, std::string &command) {
@@ -94,8 +98,7 @@
 
   LPVOID env_block = nullptr;
   ::CreateEnvironmentBuffer(launch_info.GetEnvironment(), environment);
-  if (!environment.empty())
-    env_block = environment.data();
+  env_block = environment.data();
 
   executable = launch_info.GetExecutableFile().GetPath();
   GetFlattenedWindowsCommandString(launch_info.GetArguments(), commandLine);
diff --git a/lldb/test/API/commands/settings/TestSettings.py b/lldb/test/API/commands/settings/TestSettings.py
--- a/lldb/test/API/commands/settings/TestSettings.py
+++ b/lldb/test/API/commands/settings/TestSettings.py
@@ -286,7 +286,6 @@
                 "Environment variable 'MY_ENV_VAR' successfully passed."])
 
     @skipIfRemote  # it doesn't make sense to send host env to remote target
-    @skipIf(oslist=["windows"])
     def test_pass_host_env_vars(self):
         """Test that the host env vars are passed to the launched process."""
         self.build()