Index: include/clang/Serialization/ASTReader.h
===================================================================
--- include/clang/Serialization/ASTReader.h
+++ include/clang/Serialization/ASTReader.h
@@ -478,10 +478,18 @@
   /// in the chain.
   DeclUpdateOffsetsMap DeclUpdateOffsets;
 
+  struct PendingUpdateRecord {
+    Decl *D;
+    serialization::GlobalDeclID ID;
+    // Whether the declaration was just deserialized.
+    bool JustLoaded;
+    PendingUpdateRecord(serialization::GlobalDeclID ID, Decl *D,
+                        bool JustLoaded)
+        : D(D), ID(ID), JustLoaded(JustLoaded) {}
+  };
   /// \brief Declaration updates for already-loaded declarations that we need
   /// to apply once we finish processing an import.
-  llvm::SmallVector<std::pair<serialization::GlobalDeclID, Decl*>, 16>
-      PendingUpdateRecords;
+  llvm::SmallVector<PendingUpdateRecord, 16> PendingUpdateRecords;
 
   enum class PendingFakeDefinitionKind { NotFake, Fake, FakeLoaded };
 
@@ -1279,7 +1287,7 @@
 
   RecordLocation DeclCursorForID(serialization::DeclID ID,
                                  SourceLocation &Location);
-  void loadDeclUpdateRecords(serialization::DeclID ID, Decl *D);
+  void loadDeclUpdateRecords(PendingUpdateRecord &Record);
   void loadPendingDeclChain(Decl *D, uint64_t LocalOffset);
   void loadObjCCategories(serialization::GlobalDeclID ID, ObjCInterfaceDecl *D,
                           unsigned PreviousGeneration = 0);
Index: lib/Serialization/ASTReader.cpp
===================================================================
--- lib/Serialization/ASTReader.cpp
+++ lib/Serialization/ASTReader.cpp
@@ -2757,7 +2757,8 @@
       // If we've already loaded the decl, perform the updates when we finish
       // loading this block.
       if (Decl *D = GetExistingDecl(ID))
-        PendingUpdateRecords.push_back(std::make_pair(ID, D));
+        PendingUpdateRecords.push_back(
+            PendingUpdateRecord(ID, D, /*JustLoaded=*/false));
       break;
     }
 
@@ -3087,7 +3088,8 @@
         // If we've already loaded the decl, perform the updates when we finish
         // loading this block.
         if (Decl *D = GetExistingDecl(ID))
-          PendingUpdateRecords.push_back(std::make_pair(ID, D));
+          PendingUpdateRecords.push_back(
+              PendingUpdateRecord(ID, D, /*JustLoaded=*/false));
       }
       break;
     }
@@ -8940,7 +8942,7 @@
     while (!PendingUpdateRecords.empty()) {
       auto Update = PendingUpdateRecords.pop_back_val();
       ReadingKindTracker ReadingKind(Read_Decl, *this);
-      loadDeclUpdateRecords(Update.first, Update.second);
+      loadDeclUpdateRecords(Update);
     }
   }
 
Index: lib/Serialization/ASTReaderDecl.cpp
===================================================================
--- lib/Serialization/ASTReaderDecl.cpp
+++ lib/Serialization/ASTReaderDecl.cpp
@@ -3612,7 +3612,8 @@
   assert(Record.getIdx() == Record.size());
 
   // Load any relevant update records.
-  PendingUpdateRecords.push_back(std::make_pair(ID, D));
+  PendingUpdateRecords.push_back(
+      PendingUpdateRecord(ID, D, /*JustLoaded=*/true));
 
   // Load the categories after recursive loading is finished.
   if (ObjCInterfaceDecl *Class = dyn_cast<ObjCInterfaceDecl>(D))
@@ -3657,20 +3658,24 @@
   }
 }
 
-void ASTReader::loadDeclUpdateRecords(serialization::DeclID ID, Decl *D) {
+void ASTReader::loadDeclUpdateRecords(PendingUpdateRecord &Record) {
   // The declaration may have been modified by files later in the chain.
   // If this is the case, read the record containing the updates from each file
   // and pass it to ASTDeclReader to make the modifications.
+  serialization::GlobalDeclID ID = Record.ID;
+  Decl *D = Record.D;
   ProcessingUpdatesRAIIObj ProcessingUpdates(*this);
   DeclUpdateOffsetsMap::iterator UpdI = DeclUpdateOffsets.find(ID);
   if (UpdI != DeclUpdateOffsets.end()) {
     auto UpdateOffsets = std::move(UpdI->second);
     DeclUpdateOffsets.erase(UpdI);
 
-    // FIXME: This call to isConsumerInterestedIn is not safe because
-    // we could be deserializing declarations at the moment. We should
-    // delay calling this in the same way as done in D30793.
-    bool WasInteresting = isConsumerInterestedIn(Context, D, false);
+    // Check if this decl was interesting to the consumer. If we just loaded
+    // the declaration, then we know it was interesting and we skip the call
+    // to isConsumerInterestedIn because it is unsafe to call in the
+    // current ASTReader state.
+    bool WasInteresting =
+        Record.JustLoaded || isConsumerInterestedIn(Context, D, false);
     for (auto &FileAndOffset : UpdateOffsets) {
       ModuleFile *F = FileAndOffset.first;
       uint64_t Offset = FileAndOffset.second;