diff --git a/assembly/buffer/index.ts b/assembly/buffer/index.ts
index c73f012..769dd8a 100644
--- a/assembly/buffer/index.ts
+++ b/assembly/buffer/index.ts
@@ -24,18 +24,18 @@ export class Buffer extends Uint8Array {
   }
 
   readUInt8(offset: i32 = 0): u8 {
-    if(<u32>offset > this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
+    if(<u32>offset >= this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
     return load<u8>(this.dataStart + usize(offset));
   }
 
   writeUInt8(value: u8, offset: i32 = 0): i32 {
-    if(<u32>offset > this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
+    if(<u32>offset >= this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
     store<u8>(this.dataStart + offset, value);
     return offset + 1;
   }
 
   writeInt8(value: i8, offset: i32 = 0): i32 {
-    if(<u32>offset > this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
+    if(<u32>offset >= this.dataLength) throw new RangeError(E_INDEXOUTOFRANGE);
     store<i8>(this.dataStart + offset, value);
     return offset + 1;
   }