diff --git a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
index 3e11efc0e30..9f5e0bb844d 100644
--- a/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
+++ b/lib/Transforms/Instrumentation/DataFlowSanitizer.cpp
@@ -476,7 +476,7 @@ DataFlowSanitizer::WrapperKind DataFlowSanitizer::getWrapperKind(Function *F) {
     return WK_Functional;
   if (ABIList.isIn(*F, "discard"))
     return WK_Discard;
-  if (ABIList.isIn(*F, "custom"))
+  if (ABIList.isIn(*F, "custom") && !F->isVarArg())
     return WK_Custom;
 
   return WK_Warning;
diff --git a/test/Instrumentation/DataFlowSanitizer/abilist.ll b/test/Instrumentation/DataFlowSanitizer/abilist.ll
index 66ddc140a08..53b7d86dbda 100644
--- a/test/Instrumentation/DataFlowSanitizer/abilist.ll
+++ b/test/Instrumentation/DataFlowSanitizer/abilist.ll
@@ -16,6 +16,8 @@ declare void @custom1(i32 %a, i32 %b)
 
 declare i32 @custom2(i32 %a, i32 %b)
 
+declare void @custom3(...)
+
 declare void @customcb(i32 (i32)* %cb)
 
 declare i32 @cb(i32)
@@ -33,6 +35,10 @@ define void @f() {
   ; CHECK: call void @__dfsw_customcb({{.*}} @"dfst0$customcb", i8* bitcast ({{.*}} @"dfs$cb" to i8*), i16 0)
   call void @customcb(i32 (i32)* @cb)
 
+  ; CHECK: call void @__dfsan_unimplemented
+  ; CHECK: call void (...)* @custom3()
+  call void (...)* @custom3()
+
   ret void
 }