diff --git a/lldb/source/Commands/CommandObjectProcess.cpp b/lldb/source/Commands/CommandObjectProcess.cpp
--- a/lldb/source/Commands/CommandObjectProcess.cpp
+++ b/lldb/source/Commands/CommandObjectProcess.cpp
@@ -1043,7 +1043,7 @@
     UnixSignalsSP signals = m_exe_ctx.GetProcessPtr()->GetUnixSignals();
     int signo = signals->GetFirstSignalNumber();
     while (signo != LLDB_INVALID_SIGNAL_NUMBER) {
-      request.AddCompletion(signals->GetSignalAsCString(signo), "");
+      request.TryCompleteCurrentArg(signals->GetSignalAsCString(signo));
       signo = signals->GetNextSignalNumber(signo);
     }
   }
diff --git a/lldb/test/API/functionalities/completion/TestCompletion.py b/lldb/test/API/functionalities/completion/TestCompletion.py
--- a/lldb/test/API/functionalities/completion/TestCompletion.py
+++ b/lldb/test/API/functionalities/completion/TestCompletion.py
@@ -164,6 +164,8 @@
 
         self.complete_from_to('process signal ',
                               'process signal SIG')
+        self.complete_from_to('process signal SIGIN',
+                              'process signal SIGINT')
         self.complete_from_to('process signal SIGA',
                               ['SIGABRT',
                                'SIGALRM'])