diff --git a/interface/src/Application.h b/interface/src/Application.h
index 688cf23876..9f87d05711 100644
--- a/interface/src/Application.h
+++ b/interface/src/Application.h
@@ -119,9 +119,9 @@ static const QString INFO_EDIT_ENTITIES_PATH = "html/edit-commands.html";
 
 #ifdef Q_OS_WIN
 static const UINT UWM_IDENTIFY_INSTANCES = 
-    RegisterWindowMessage("UWM_IDENTIFY_INSTANCES_{8AB82783-B74A-4258-955B-8188C22AA0D6}");
+    RegisterWindowMessage("UWM_IDENTIFY_INSTANCES_{8AB82783-B74A-4258-955B-8188C22AA0D6}_" + qgetenv("USERNAME"));
 static const UINT UWM_SHOW_APPLICATION =
-    RegisterWindowMessage("UWM_SHOW_APPLICATION_{71123FD6-3DA8-4DC1-9C27-8A12A6250CBA}");
+    RegisterWindowMessage("UWM_SHOW_APPLICATION_{71123FD6-3DA8-4DC1-9C27-8A12A6250CBA}_" + qgetenv("USERNAME"));
 #endif
 
 class Application;
diff --git a/interface/src/main.cpp b/interface/src/main.cpp
index 7d80b077b8..7112944375 100644
--- a/interface/src/main.cpp
+++ b/interface/src/main.cpp
@@ -42,7 +42,7 @@ static BOOL CALLBACK enumWindowsCallback(HWND hWnd, LPARAM lParam) {
 int main(int argc, const char* argv[]) {
 #ifdef Q_OS_WIN
     // Run only one instance of Interface at a time.
-    HANDLE mutex = CreateMutex(NULL, FALSE, "High Fidelity Interface");
+    HANDLE mutex = CreateMutex(NULL, FALSE, "High Fidelity Interface - " + qgetenv("USERNAME"));
     DWORD result = GetLastError();
     if (result == ERROR_ALREADY_EXISTS || result == ERROR_ACCESS_DENIED) {
         // Interface is already running.