diff --git a/mlir/test/mlir-tblgen/op-decl.td b/mlir/test/mlir-tblgen/op-decl.td
--- a/mlir/test/mlir-tblgen/op-decl.td
+++ b/mlir/test/mlir-tblgen/op-decl.td
@@ -76,7 +76,7 @@
 // CHECK:   ::mlir::Operation::result_range getODSResults(unsigned index);
 // CHECK:   ::mlir::Value r();
 // CHECK:   ::mlir::Region &someRegion();
-// CHECK:   ::mlir::MutableArrayRef<Region> someRegions();
+// CHECK:   ::mlir::MutableArrayRef<::mlir::Region> someRegions();
 // CHECK:   ::mlir::IntegerAttr attr1Attr()
 // CHECK:   uint32_t attr1();
 // CHECK:   ::mlir::FloatAttr attr2Attr()
diff --git a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
--- a/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
+++ b/mlir/tools/mlir-tblgen/OpDefinitionsGen.cpp
@@ -1014,8 +1014,8 @@
 
     // Generate the accessors for a variadic region.
     if (region.isVariadic()) {
-      auto *m = opClass.addMethodAndPrune("::mlir::MutableArrayRef<Region>",
-                                          region.name);
+      auto *m = opClass.addMethodAndPrune(
+          "::mlir::MutableArrayRef<::mlir::Region>", region.name);
       m->body() << formatv("  return (*this)->getRegions().drop_front({0});",
                            i);
       continue;