diff --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -2669,12 +2669,12 @@
 }
 
 unsigned ASTWriter::getSubmoduleID(Module *Mod) {
+  unsigned ID = getLocalOrImportedSubmoduleID(Mod);
   // FIXME: This can easily happen, if we have a reference to a submodule that
   // did not result in us loading a module file for that submodule. For
   // instance, a cross-top-level-module 'conflict' declaration will hit this.
-  unsigned ID = getLocalOrImportedSubmoduleID(Mod);
-  assert((ID || !Mod) &&
-         "asked for module ID for non-local, non-imported module");
+  // assert((ID || !Mod) &&
+  //        "asked for module ID for non-local, non-imported module");
   return ID;
 }