Index: lit/Process/Inputs/env.cpp
===================================================================
--- lit/Process/Inputs/env.cpp
+++ lit/Process/Inputs/env.cpp
@@ -0,0 +1,7 @@
+#include <cstdlib>
+#include <iostream>
+
+int main() {
+  if (const char *env_p = std::getenv("FOO"))
+    std::cout << "FOO=" << env_p << '\n';
+}
Index: lit/Process/TestEnvironment.test
===================================================================
--- lit/Process/TestEnvironment.test
+++ lit/Process/TestEnvironment.test
@@ -0,0 +1,7 @@
+The double quotes around "BAR" ensure we don't match the command.
+
+RUN: %clangxx -std=c++11 %p/Inputs/env.cpp -o %t
+RUN: %lldb %t -o 'process launch --environment FOO="BAR"' | FileCheck %s
+RUN: %lldb %t -o 'env FOO="BAR"' -o 'process launch' | FileCheck %s
+
+CHECK: FOO=BAR
Index: source/Commands/CommandObjectProcess.cpp
===================================================================
--- source/Commands/CommandObjectProcess.cpp
+++ source/Commands/CommandObjectProcess.cpp
@@ -193,7 +193,10 @@
     if (target->GetDisableSTDIO())
       m_options.launch_info.GetFlags().Set(eLaunchFlagDisableSTDIO);
 
-    m_options.launch_info.GetEnvironment() = target->GetEnvironment();
+    // Merge the launch info environment with the target environment.
+    Environment target_env = target->GetEnvironment();
+    m_options.launch_info.GetEnvironment().insert(target_env.begin(),
+                                                  target_env.end());
 
     if (!target_settings_argv0.empty()) {
       m_options.launch_info.GetArguments().AppendArgument(