diff --git a/mlir/include/mlir/Dialect/Quant/QuantTypes.h b/mlir/include/mlir/Dialect/Quant/QuantTypes.h
index de5aed0a91a20..09cddf3e96f4d 100644
--- a/mlir/include/mlir/Dialect/Quant/QuantTypes.h
+++ b/mlir/include/mlir/Dialect/Quant/QuantTypes.h
@@ -52,7 +52,8 @@ class QuantizedType : public Type {
   using Type::Type;
 
   /// The maximum number of bits supported for storage types.
-  static constexpr unsigned MaxStorageBits = 32;
+  /// NOTE: u64 storage type is not yet supported.
+  static constexpr unsigned MaxStorageBits = 64;
 
   static LogicalResult verify(function_ref<InFlightDiagnostic()> emitError,
                               unsigned flags, Type storageType,
diff --git a/mlir/lib/Dialect/Quant/IR/QuantTypes.cpp b/mlir/lib/Dialect/Quant/IR/QuantTypes.cpp
index 81e3b914755be..cb8be7d39ef35 100644
--- a/mlir/lib/Dialect/Quant/IR/QuantTypes.cpp
+++ b/mlir/lib/Dialect/Quant/IR/QuantTypes.cpp
@@ -44,15 +44,21 @@ QuantizedType::verify(function_ref<InFlightDiagnostic()> emitError,
   if (integralWidth == 0 || integralWidth > MaxStorageBits)
     return emitError() << "illegal storage type size: " << integralWidth;
 
-  // Verify storageTypeMin and storageTypeMax.
   bool isSigned =
       (flags & QuantizationFlags::Signed) == QuantizationFlags::Signed;
+  // u64 is not yet supported because its full range cannot be represented
+  // by the type of `storageTypeMax`, making it difficult to verify the
+  // storage type.
+  if (!isSigned && integralWidth == 64)
+    return emitError()
+           << "illegal storage type; u64 storage type is not supported";
+
+  // Verify storageTypeMin and storageTypeMax.
   int64_t defaultIntegerMin =
       getDefaultMinimumForInteger(isSigned, integralWidth);
   int64_t defaultIntegerMax =
       getDefaultMaximumForInteger(isSigned, integralWidth);
-  if (storageTypeMax - storageTypeMin <= 0 ||
-      storageTypeMin < defaultIntegerMin ||
+  if (storageTypeMax <= storageTypeMin || storageTypeMin < defaultIntegerMin ||
       storageTypeMax > defaultIntegerMax) {
     return emitError() << "illegal storage min and storage max: ("
                        << storageTypeMin << ":" << storageTypeMax << ")";
diff --git a/mlir/test/Dialect/Quant/parse-any-invalid.mlir b/mlir/test/Dialect/Quant/parse-any-invalid.mlir
index 41c5f93070717..a7c7f461846a4 100644
--- a/mlir/test/Dialect/Quant/parse-any-invalid.mlir
+++ b/mlir/test/Dialect/Quant/parse-any-invalid.mlir
@@ -26,12 +26,12 @@
 !qalias = !quant.any<i<-4:3>:f32>
 
 // -----
-// Unrecognized storage type: storage size > 32
-// expected-error@+1 {{illegal storage type size: 33}}
-!qalias = !quant.any<i33:f32>
+// Unrecognized storage type: storage size > 64
+// expected-error@+1 {{illegal storage type size: 65}}
+!qalias = !quant.any<i65:f32>
 
 // -----
-// Unrecognized storage type: storage size < 0
+// Unrecognized storage type: storage size > 64
 // expected-error@+1 {{illegal storage type size: 1024}}
 !qalias = !quant.any<i1024<-4:3>:f32>
 
diff --git a/mlir/test/Dialect/Quant/parse-uniform-invalid.mlir b/mlir/test/Dialect/Quant/parse-uniform-invalid.mlir
index a82e8efdb1a3c..5f7ac004c49b9 100644
--- a/mlir/test/Dialect/Quant/parse-uniform-invalid.mlir
+++ b/mlir/test/Dialect/Quant/parse-uniform-invalid.mlir
@@ -46,9 +46,9 @@
 !qalias = !quant.uniform<i<-4:3>:f32, 0.99872:127>
 
 // -----
-// Unrecognized storage type: storage size > 32
-// expected-error@+1 {{illegal storage type size: 33}}
-!qalias = !quant.uniform<i33:f32, 0.99872:127>
+// Unrecognized storage type: storage size > 64
+// expected-error@+1 {{illegal storage type size: 65}}
+!qalias = !quant.uniform<i65:f32, 0.99872:127>
 
 // -----
 // Unrecognized storage type: storage size < 0
@@ -60,6 +60,11 @@
 // expected-error@+1 {{invalid integer width}}
 !qalias = !quant.uniform<i123123123120<-4:3>:f32, 0.99872:127>
 
+// -----
+// Illegal storage type: u64
+// expected-error@+1 {{illegal storage type; u64 storage type is not supported}}
+!qalias = !quant.uniform<u64:f32, 0.99782:127>
+
 // -----
 // Illegal storage min/max: max - min < 0
 // expected-error@+1 {{illegal storage min and storage max: (2:1)}}
diff --git a/mlir/test/Dialect/Quant/parse-uniform.mlir b/mlir/test/Dialect/Quant/parse-uniform.mlir
index 4fbe86d935ea3..5bc391e9ea8ca 100644
--- a/mlir/test/Dialect/Quant/parse-uniform.mlir
+++ b/mlir/test/Dialect/Quant/parse-uniform.mlir
@@ -83,6 +83,15 @@ func.func @parse() -> !qalias {
   return %0 : !qalias
 }
 
+// -----
+// Storage type: i64
+// CHECK: !quant.uniform<i64:f32, 2.000000e+02>
+!qalias = !quant.uniform<i64:f32, 2.0e+2>
+func.func @parse() -> !qalias {
+  %0 = "foo"() : () -> !qalias
+  return %0 : !qalias
+}
+
 // -----
 // Expressed type: f32
 // CHECK: !quant.uniform<u8:f32, 2.000000e+02>