diff --git a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
--- a/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
+++ b/mlir/lib/Conversion/MemRefToLLVM/MemRefToLLVM.cpp
@@ -454,9 +454,17 @@
         initialValue = elementsAttr.getValue({});
     }
 
-    rewriter.replaceOpWithNewOp<LLVM::GlobalOp>(
+    auto newGlobal = rewriter.replaceOpWithNewOp<LLVM::GlobalOp>(
         global, arrayTy, global.constant(), linkage, global.sym_name(),
         initialValue, /*alignment=*/0, type.getMemorySpaceAsInt());
+    if (!global.isExternal() && global.isUninitialized()) {
+      Block *blk = new Block();
+      newGlobal.getInitializerRegion().push_back(blk);
+      rewriter.setInsertionPointToStart(blk);
+      Value undef[] = {
+          rewriter.create<LLVM::UndefOp>(global.getLoc(), arrayTy)};
+      rewriter.create<LLVM::ReturnOp>(global.getLoc(), undef);
+    }
     return success();
   }
 };
diff --git a/mlir/test/Conversion/MemRefToLLVM/memref-to-llvm.mlir b/mlir/test/Conversion/MemRefToLLVM/memref-to-llvm.mlir
--- a/mlir/test/Conversion/MemRefToLLVM/memref-to-llvm.mlir
+++ b/mlir/test/Conversion/MemRefToLLVM/memref-to-llvm.mlir
@@ -623,7 +623,10 @@
 
 // -----
 
-// CHECK: llvm.mlir.global external @gv0() : !llvm.array<2 x f32>
+// CHECK:   llvm.mlir.global external @gv0() : !llvm.array<2 x f32> {
+// CHECK-NEXT:     %0 = llvm.mlir.undef : !llvm.array<2 x f32>
+// CHECK-NEXT:     llvm.return %0 : !llvm.array<2 x f32>
+// CHECK-NEXT:   }
 memref.global @gv0 : memref<2xf32> = uninitialized
 
 // CHECK: llvm.mlir.global private @gv1() : !llvm.array<2 x f32>