diff --git a/common/workflow-core/src/main/scala/org/apache/texera/amber/util/ArrowUtils.scala b/common/workflow-core/src/main/scala/org/apache/texera/amber/util/ArrowUtils.scala
index c4f649e719e..af14ae9acd0 100644
--- a/common/workflow-core/src/main/scala/org/apache/texera/amber/util/ArrowUtils.scala
+++ b/common/workflow-core/src/main/scala/org/apache/texera/amber/util/ArrowUtils.scala
@@ -131,8 +131,13 @@ object ArrowUtils extends LazyLogging {
           case 16 | 32 =>
             AttributeType.INTEGER
 
-          case 64 | _ =>
+          case 64 =>
             AttributeType.LONG
+
+          case other =>
+            throw new AttributeTypeUtils.AttributeTypeException(
+              s"Unsupported Int bit width: $other"
+            )
         }
       case _: ArrowType.Bool =>
         AttributeType.BOOLEAN
@@ -187,10 +192,15 @@ object ArrowUtils extends LazyLogging {
                 .asInstanceOf[IntVector]
                 .setSafe(index, !isNull, if (isNull) 0 else value.asInstanceOf[Int])
 
-            case 64 | _ =>
+            case 64 =>
               vector
                 .asInstanceOf[BigIntVector]
                 .setSafe(index, !isNull, if (isNull) 0 else value.asInstanceOf[Long])
+
+            case other =>
+              throw new AttributeTypeUtils.AttributeTypeException(
+                s"Unsupported Int bit width: $other"
+              )
           }
 
         case _: ArrowType.Bool =>
diff --git a/common/workflow-core/src/test/scala/org/apache/texera/amber/util/ArrowUtilsSpec.scala b/common/workflow-core/src/test/scala/org/apache/texera/amber/util/ArrowUtilsSpec.scala
index 212be040b12..62b10a66864 100644
--- a/common/workflow-core/src/test/scala/org/apache/texera/amber/util/ArrowUtilsSpec.scala
+++ b/common/workflow-core/src/test/scala/org/apache/texera/amber/util/ArrowUtilsSpec.scala
@@ -45,14 +45,16 @@ class ArrowUtilsSpec extends AnyFlatSpec with Matchers {
     ArrowUtils.toAttributeType(new ArrowType.Int(64, true)) shouldBe AttributeType.LONG
   }
 
-  it should "map non-standard Int bit-widths to LONG (current behavior)" in {
-    // Pin: the source code's match is `case 16 | 32 => INTEGER` then
-    // `case 64 | _ => LONG`. The trailing `_` makes the second arm a
-    // catch-all, so Int(8), Int(128) and any other width all surface as
-    // LONG. A future fix that distinguishes those widths will deliberately
-    // break this spec.
-    ArrowUtils.toAttributeType(new ArrowType.Int(8, true)) shouldBe AttributeType.LONG
-    ArrowUtils.toAttributeType(new ArrowType.Int(128, true)) shouldBe AttributeType.LONG
+  it should "throw AttributeTypeException for non-standard Int bit-widths" in {
+    // Only 16/32 (INTEGER) and 64 (LONG) are supported. Other widths used to
+    // be silently coerced to LONG by a `case 64 | _` catch-all; they now
+    // raise rather than masquerade as Int64.
+    assertThrows[AttributeTypeException] {
+      ArrowUtils.toAttributeType(new ArrowType.Int(8, true))
+    }
+    assertThrows[AttributeTypeException] {
+      ArrowUtils.toAttributeType(new ArrowType.Int(128, true))
+    }
   }
 
   it should "map Bool to BOOLEAN" in {