Index: lib/StaticAnalyzer/Core/RegionStore.cpp
===================================================================
--- lib/StaticAnalyzer/Core/RegionStore.cpp
+++ lib/StaticAnalyzer/Core/RegionStore.cpp
@@ -1674,7 +1674,8 @@
 
     // Lazy bindings are usually handled through getExistingLazyBinding().
     // We should unify these two code paths at some point.
-    if (val.getAs<nonloc::LazyCompoundVal>())
+    if (val.getAs<nonloc::LazyCompoundVal>() ||
+        val.getAs<nonloc::CompoundVal>())
       return val;
 
     llvm_unreachable("Unknown default value");
Index: test/Analysis/uninit-vals-union.c
===================================================================
--- /dev/null
+++ test/Analysis/uninit-vals-union.c
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -analyze -analyzer-checker=core.builtin -analyzer-store=region -verify -Wno-unused %s
+
+typedef union {
+  int y;
+} U;
+
+typedef struct { int x; } A;
+
+void foo() {
+  U u = {};
+  A *a = &u; // expected-warning{{incompatible pointer types}}
+  a->x;      // no-crash
+}