Index: lib/Format/ContinuationIndenter.cpp
===================================================================
--- lib/Format/ContinuationIndenter.cpp
+++ lib/Format/ContinuationIndenter.cpp
@@ -919,6 +919,12 @@
     NewParenState.NoLineBreak =
         NewParenState.NoLineBreak || State.Stack.back().NoLineBreakInOperand;
 
+    // Don't propagate AvoidBinPacking into subexpressions of arg/param lists.
+    if (Current.FakeLParens.size() > 0 &&
+        Current.FakeLParens.back() > prec::Comma) {
+      NewParenState.AvoidBinPacking = false;
+    }
+
     // Indent from 'LastSpace' unless these are fake parentheses encapsulating
     // a builder type call after 'return' or, if the alignment after opening
     // brackets is disabled.
Index: unittests/Format/FormatTest.cpp
===================================================================
--- unittests/Format/FormatTest.cpp
+++ unittests/Format/FormatTest.cpp
@@ -2591,6 +2591,30 @@
                Style);
 }
 
+TEST_F(FormatTest, AllowBinPackingInsideArguments) {
+  FormatStyle Style = getLLVMStyle();
+  Style.AlignAfterOpenBracket = FormatStyle::BAS_AlwaysBreak;
+  Style.BreakBeforeBinaryOperators = FormatStyle::BOS_NonAssignment;
+  Style.BinPackArguments = false;
+  Style.BinPackParameters = false;
+  verifyFormat(StringRef(R"(
+someFunction(
+    arg1,
+    arg2,
+    arg3____________________________ + is + quite + long + so + it
+        + f(and_even,
+            the,
+            arguments << of << its << subexpressions << lengthy << as << they
+                      << may << or__ << may,
+            not__,
+            be)
+        + a + r + e / l + o + v + i + n + g + l + y / b + i + n - p + a + c + k
+        + e + d,
+    arg4,
+    arg5);
+               )").trim(), Style);
+}
+
 TEST_F(FormatTest, ConstructorInitializers) {
   verifyFormat("Constructor() : Initializer(FitsOnTheLine) {}");
   verifyFormat("Constructor() : Inttializer(FitsOnTheLine) {}",