diff --git a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
--- a/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
+++ b/mlir/lib/Target/LLVMIR/ModuleTranslation.cpp
@@ -825,7 +825,7 @@
     if (value.empty())
       return emitError(loc) << "LLVM attribute '" << key << "' expects a value";
 
-    int result;
+    int64_t result;
     if (!value.getAsInteger(/*Radix=*/0, result))
       llvmFunc->addFnAttr(
           llvm::Attribute::get(llvmFunc->getContext(), kind, result));
diff --git a/mlir/test/Target/LLVMIR/llvmir.mlir b/mlir/test/Target/LLVMIR/llvmir.mlir
--- a/mlir/test/Target/LLVMIR/llvmir.mlir
+++ b/mlir/test/Target/LLVMIR/llvmir.mlir
@@ -1727,6 +1727,15 @@
 
 // -----
 
+// CHECK-LABEL: @my_allocator
+// CHECK: #[[ALLOC_ATTRS:[0-9]*]]
+llvm.func @my_allocator(i64) attributes {passthrough = [["allocsize", "4294967295"]]}
+
+// CHECK: attributes #[[ALLOC_ATTRS]] = {
+// CHECK-DAG: allocsize(0)
+
+// -----
+
 // CHECK-LABEL: @functionEntryCount
 // CHECK-SAME: !prof ![[PROF_ID:[0-9]*]]
 llvm.func @functionEntryCount() attributes {function_entry_count = 4242 : i64} {