diff --git a/mlir/include/mlir/IR/Builders.h b/mlir/include/mlir/IR/Builders.h
--- a/mlir/include/mlir/IR/Builders.h
+++ b/mlir/include/mlir/IR/Builders.h
@@ -374,6 +374,10 @@
   template <typename OpTy, typename... Args>
   OpTy create(Location location, Args &&... args) {
     OperationState state(location, OpTy::getOperationName());
+    if (!state.name.getAbstractOperation())
+      llvm::report_fatal_error("Building op `" +
+                               state.name.getStringRef().str() +
+                               "` but it isn't registered in this MLIRContext");
     OpTy::build(*this, state, std::forward<Args>(args)...);
     auto *op = createOperation(state);
     auto result = dyn_cast<OpTy>(op);
@@ -390,6 +394,10 @@
     // Create the operation without using 'createOperation' as we don't want to
     // insert it yet.
     OperationState state(location, OpTy::getOperationName());
+    if (!state.name.getAbstractOperation())
+      llvm::report_fatal_error("Building op `" +
+                               state.name.getStringRef().str() +
+                               "` but it isn't registered in this MLIRContext");
     OpTy::build(*this, state, std::forward<Args>(args)...);
     Operation *op = Operation::create(state);
 
diff --git a/mlir/include/mlir/IR/OpDefinition.h b/mlir/include/mlir/IR/OpDefinition.h
--- a/mlir/include/mlir/IR/OpDefinition.h
+++ b/mlir/include/mlir/IR/OpDefinition.h
@@ -1235,7 +1235,9 @@
   static bool classof(Operation *op) {
     if (auto *abstractOp = op->getAbstractOperation())
       return TypeID::get<ConcreteType>() == abstractOp->typeID;
-    return op->getName().getStringRef() == ConcreteType::getOperationName();
+    llvm_unreachable(Twine("Can't cast to unregistered operation") +
+                     ConcreteType::getOperationName());
+    return false;
   }
 
   /// This is the hook used by the AsmParser to parse the custom form of this
diff --git a/mlir/lib/IR/MLIRContext.cpp b/mlir/lib/IR/MLIRContext.cpp
--- a/mlir/lib/IR/MLIRContext.cpp
+++ b/mlir/lib/IR/MLIRContext.cpp
@@ -621,8 +621,9 @@
 static Dialect &lookupDialectForSymbol(MLIRContext *ctx, TypeID typeID) {
   auto &impl = ctx->getImpl();
   auto it = impl.registeredDialectSymbols.find(typeID);
-  assert(it != impl.registeredDialectSymbols.end() &&
-         "symbol is not registered.");
+  if (it == impl.registeredDialectSymbols.end())
+    llvm::report_fatal_error(
+        "Trying to create a type that was not registered in this MLIRContext.");
   return *it->second;
 }