Index: lib/AST/ExprConstant.cpp
===================================================================
--- lib/AST/ExprConstant.cpp
+++ lib/AST/ExprConstant.cpp
@@ -7419,7 +7419,10 @@
     // If we don't know the array bound, conservatively assume we're looking at
     // the final array element.
     ++I;
-    BaseType = BaseType->castAs<PointerType>()->getPointeeType();
+    if (BaseType->isIncompleteArrayType())
+      BaseType = Ctx.getAsArrayType(BaseType)->getElementType();
+    else
+      BaseType = BaseType->castAs<PointerType>()->getPointeeType();
   }
 
   for (unsigned E = LVal.Designator.Entries.size(); I != E; ++I) {
Index: test/Sema/builtin-object-size.c
===================================================================
--- test/Sema/builtin-object-size.c
+++ test/Sema/builtin-object-size.c
@@ -91,3 +91,16 @@
 
   return n;
 }
+
+typedef struct 	 {
+  char string[512];
+} NestedArrayStruct;
+
+typedef struct 	 {
+    int x;
+    NestedArrayStruct	session[];
+} IncompleteArrayStruct;
+
+void rd36094951_IAS_builtin_object_size_assertion(IncompleteArrayStruct* p) {
+   __builtin___strlcpy_chk (p->session[0].string, "ab", 2, __builtin_object_size(p->session[0].string, 1));
+}