diff --git a/lldb/source/Host/common/Editline.cpp b/lldb/source/Host/common/Editline.cpp
--- a/lldb/source/Host/common/Editline.cpp
+++ b/lldb/source/Host/common/Editline.cpp
@@ -1004,7 +1004,8 @@
     case CompletionMode::Normal: {
       std::string to_add = completion.GetCompletion();
       to_add = to_add.substr(request.GetCursorArgumentPrefix().size());
-      if (request.GetParsedArg().IsQuoted())
+      // Terminate the current argument with a quote if it started with a quote.
+      if (!request.GetParsedLine().empty() && request.GetParsedArg().IsQuoted())
         to_add.push_back(request.GetParsedArg().GetQuoteChar());
       to_add.push_back(' ');
       el_insertstr(m_editline, to_add.c_str());
diff --git a/lldb/test/API/commands/expression/multiline-completion/TestMultilineCompletion.py b/lldb/test/API/commands/expression/multiline-completion/TestMultilineCompletion.py
--- a/lldb/test/API/commands/expression/multiline-completion/TestMultilineCompletion.py
+++ b/lldb/test/API/commands/expression/multiline-completion/TestMultilineCompletion.py
@@ -11,6 +11,21 @@
 
     mydir = TestBase.compute_mydir(__file__)
 
+    def start_expression_editor(self):
+        """ Starts the multiline expression editor. """
+        self.child.send("expression\n")
+        self.child.expect_exact("terminate with an empty line to evaluate")
+
+    def exit_expression_editor(self):
+        """ Exits the multiline expression editor. """
+        # Send a newline to finish the current line. The second newline will
+        # finish the new empty line which will exit the editor. The space at the
+        # start prevents that the first newline already exits the editor (in
+        # case the current line of the editor is already empty when this
+        # function is called).
+        self.child.send(" \n\n")
+        self.expect_prompt()
+
     # PExpect uses many timeouts internally and doesn't play well
     # under ASAN on a loaded machine..
     @skipIfAsan
@@ -21,14 +36,23 @@
 
         self.launch(executable=self.getBuildArtifact("a.out"), dimensions=(100,500))
         self.expect("b main", substrs=["Breakpoint 1", "address ="])
-        self.expect("run", substrs=["stop reason ="])
+        self.expect("run", substrs=["stop reason = breakpoint 1"])
 
-        self.child.sendline("expr")
-        self.child.expect_exact("terminate with an empty line to evaluate")
+        self.start_expression_editor()
         self.child.send("to_\t")
         self.child.expect_exact("to_complete")
-
-        self.child.send("\n\n")
-        self.expect_prompt()
+        self.exit_expression_editor()
+
+        # Check that completion empty input in a function with only one
+        # local variable works.
+        self.expect("breakpoint set -p 'break in single_local_func'",
+                    substrs=["Breakpoint 2"])
+        self.expect("continue", substrs=["stop reason = breakpoint 2"])
+        self.start_expression_editor()
+        self.child.send("\t")
+        # Only one local, so this will directly insert 'only_local' with a
+        # trailing space to signal a final completion.
+        self.child.expect_exact("only_local ")
+        self.exit_expression_editor()
 
         self.quit()
diff --git a/lldb/test/API/commands/expression/multiline-completion/main.c b/lldb/test/API/commands/expression/multiline-completion/main.c
--- a/lldb/test/API/commands/expression/multiline-completion/main.c
+++ b/lldb/test/API/commands/expression/multiline-completion/main.c
@@ -1,4 +1,11 @@
+int single_local_func() {
+  // This function should always only have a single local variable and no
+  // parameters.
+  int only_local = 3;
+  return only_local; // break in single_local_func
+}
+
 int main(int argc, char **argv) {
   int to_complete = 0;
-  return to_complete;
+  return to_complete + single_local_func();
 }