diff --git a/lib/Analysis/DebugInfo.cpp b/lib/Analysis/DebugInfo.cpp
index 585a087a02a..e30c0a9b330 100644
--- a/lib/Analysis/DebugInfo.cpp
+++ b/lib/Analysis/DebugInfo.cpp
@@ -68,7 +68,7 @@ uint64_t DIDescriptor::getUInt64Field(unsigned Elt) const {
     return 0;
 
   if (Elt < DbgNode->getNumOperands())
-    if (ConstantInt *CI = dyn_cast<ConstantInt>(DbgNode->getOperand(Elt)))
+    if (ConstantInt *CI = dyn_cast_or_null<ConstantInt>(DbgNode->getOperand(Elt)))
       return CI->getZExtValue();
 
   return 0;
diff --git a/test/DebugInfo/bug_null_debuginfo.ll b/test/DebugInfo/bug_null_debuginfo.ll
new file mode 100644
index 00000000000..a7fdf70d71c
--- /dev/null
+++ b/test/DebugInfo/bug_null_debuginfo.ll
@@ -0,0 +1,6 @@
+; RUN: llc
+
+
+!llvm.dbg.cu = !{!0}
+
+!0 = metadata !{null, null, null}