diff --git a/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp b/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
--- a/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
+++ b/mlir/lib/Conversion/StandardToLLVM/StandardToLLVM.cpp
@@ -1521,7 +1521,7 @@
 
     Optional<int64_t> allocationAlignment = getAllocationAlignment(allocOp);
     // Whether to use std lib function aligned_alloc that supports alignment.
-    bool useAlignedAlloc = allocationAlignment.hasValue();
+    bool useAlignedAlloc = allocationAlignment && *allocationAlignment != 0;
 
     // Insert the malloc/aligned_alloc declaration if it is not already present.
     auto allocFuncName = useAlignedAlloc ? "aligned_alloc" : "malloc";
diff --git a/mlir/test/Conversion/StandardToLLVM/convert-dynamic-memref-ops.mlir b/mlir/test/Conversion/StandardToLLVM/convert-dynamic-memref-ops.mlir
--- a/mlir/test/Conversion/StandardToLLVM/convert-dynamic-memref-ops.mlir
+++ b/mlir/test/Conversion/StandardToLLVM/convert-dynamic-memref-ops.mlir
@@ -182,6 +182,13 @@
   // ALIGNED-ALLOC:  %[[c128:.*]] = llvm.mlir.constant(128 : i64) : !llvm.i64
   // ALIGNED-ALLOC:  llvm.call @aligned_alloc(%[[c128]]
   %6 = alloc(%N) : memref<?xvector<18xf32>>
+  // When alignment is 0, revert to malloc behavior
+  // ALIGNED-ALLOC:  %[[c64:.*]] = llvm.mlir.constant(64 : index) : !llvm.i64
+  // ALIGNED-ALLOC:  llvm.mul %[[c64]]
+  // ALIGNED-ALLOC:  llvm.add
+  // ALIGNED-ALLOC-NEXT:  %[[ZERO_ALIGNED:.*]] = llvm.sub
+  // ALIGNED-ALLOC-NEXT:  llvm.call @malloc(%[[ZERO_ALIGNED]])
+  %7 = alloc() {alignment = 0} : memref<64xf32>
   return %0 : memref<32x18xf32>
 }