diff --git a/lib/Serialization/Serialization.cpp b/lib/Serialization/Serialization.cpp
index 527bfc337df14..a0b4b8d9eeac6 100644
--- a/lib/Serialization/Serialization.cpp
+++ b/lib/Serialization/Serialization.cpp
@@ -3604,7 +3604,6 @@ class DeclGroupNameContext {
         return NullGroupName;
       StringRef FileName = llvm::sys::path::filename(FullPath);
       auto Found = pMap->find(FileName);
-      assert(Found != pMap->end() && "A source file is not grouped.");
       return Found == pMap->end() ? NullGroupName : Found->second;
     }
   };