diff --git a/mlir/include/mlir/Dialect/Transform/IR/TransformOps.td b/mlir/include/mlir/Dialect/Transform/IR/TransformOps.td
--- a/mlir/include/mlir/Dialect/Transform/IR/TransformOps.td
+++ b/mlir/include/mlir/Dialect/Transform/IR/TransformOps.td
@@ -203,10 +203,14 @@
                        OptionalAttr<StrArrayAttr>:$illegal_dialects,
                        UnitAttr:$partialConversion);
   let results = (outs);
-  let regions = (region VariadicRegion<MaxSizedRegion<1>>:$regions);
+  let regions = (region
+      MaxSizedRegion<1>:$patterns,
+      VariadicRegion<MaxSizedRegion<1>>:$default_type_converter_region);
 
   let assemblyFormat = [{
-    `to` $target $regions attr-dict `:` type($target)
+    `to` $target $patterns
+    (`with` `type_converter` $default_type_converter_region^)?
+    attr-dict `:` type($target)
   }];
   let hasVerifier = 1;
 
@@ -221,15 +225,11 @@
   ];
 
   let extraClassDeclaration = [{
-    ::mlir::Region &getPatterns() {
-      return getRegion(0);
-    }
-
     ::mlir::transform::TypeConverterBuilderOpInterface getDefaultTypeConverter() {
-      if (getNumRegions() < 2)
+      if (getDefaultTypeConverterRegion().size() == 0)
         return {};
       return ::llvm::cast<::mlir::transform::TypeConverterBuilderOpInterface>(
-          &getRegion(1).front().front());
+          &getDefaultTypeConverterRegion()[0].front().front());
     }
   }];
 }
diff --git a/mlir/test/Dialect/Transform/test-pattern-application.mlir b/mlir/test/Dialect/Transform/test-pattern-application.mlir
--- a/mlir/test/Dialect/Transform/test-pattern-application.mlir
+++ b/mlir/test/Dialect/Transform/test-pattern-application.mlir
@@ -248,7 +248,7 @@
   %0 = transform.structured.match ops{["func.func"]} in %arg1 : (!transform.any_op) -> !transform.any_op
   transform.apply_conversion_patterns to %0 {
     transform.apply_conversion_patterns.transform.test_conversion_patterns
-  }, {
+  } with type_converter {
     transform.apply_conversion_patterns.transform.test_type_converter
   } {illegal_ops = ["test.foo"],
      legal_ops = ["func.func", "func.return", "test.new_op"]}
@@ -263,7 +263,7 @@
   // expected-error @below{{conversion target is not specified}}
   transform.apply_conversion_patterns to %0 {
     transform.apply_conversion_patterns.transform.test_conversion_patterns
-  }, {
+  } with type_converter {
     transform.apply_conversion_patterns.transform.test_type_converter
   } : !transform.any_op
 }