Index: lib/Support/CommandLine.cpp
===================================================================
--- lib/Support/CommandLine.cpp
+++ lib/Support/CommandLine.cpp
@@ -671,10 +671,13 @@
     StringRef OneArgName = Arg.substr(0, Length);
     Arg = Arg.substr(Length);
 
-    // Because ValueRequired is an invalid flag for grouped arguments,
-    // we don't need to pass argc/argv in.
-    assert(PGOpt->getValueExpectedFlag() != cl::ValueRequired &&
-           "Option can not be cl::Grouping AND cl::ValueRequired!");
+    if (PGOpt->getValueExpectedFlag() == cl::ValueRequired) {
+      ErrorParsing |= PGOpt->error("may not occur within a group!");
+      return nullptr;
+    }
+
+    // Because the value for the option is not required, we don't need to pass
+    // argc/argv in.
     int Dummy = 0;
     ErrorParsing |=
         ProvideOption(PGOpt, OneArgName, StringRef(), 0, nullptr, Dummy);
Index: unittests/Support/CommandLineTest.cpp
===================================================================
--- unittests/Support/CommandLineTest.cpp
+++ unittests/Support/CommandLineTest.cpp
@@ -1128,4 +1128,25 @@
   EXPECT_TRUE(MacroDefs.front().compare("HAVE_FOO") == 0);
 }
 
+TEST(CommandLineTest, GroupingWithValue) {
+  cl::ResetCommandLineParser();
+
+  StackOption<bool> OptF("f", cl::Grouping, cl::desc("Some flag"));
+  StackOption<std::string> OptV("v", cl::Grouping,
+                                cl::desc("Grouping option with a value"));
+
+  // Should be possible to use an option which requires a value
+  // at the end of a group.
+  const char *args1[] = {"prog", "-fv", "val1"};
+  EXPECT_TRUE(
+      cl::ParseCommandLineOptions(3, args1, StringRef(), &llvm::nulls()));
+  EXPECT_STREQ("val1", OptV.c_str());
+  cl::ResetAllOptionOccurrences();
+
+  // Should not crash if it is accidentally used in the middle of a group.
+  const char *args2[] = {"prog", "-vf", "val2"};
+  EXPECT_FALSE(
+      cl::ParseCommandLineOptions(3, args2, StringRef(), &llvm::nulls()));
+}
+
 }  // anonymous namespace