diff --git a/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h b/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
index 575eb77a98..ba0e01bce5 100644
--- a/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
+++ b/Userland/Libraries/LibJS/Runtime/ArrayBuffer.h
@@ -76,7 +76,7 @@ public:
     template<typename type>
     void set_value(size_t byte_index, Value value, bool is_typed_array, Order, bool is_little_endian = true);
     template<typename T>
-    Value get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true);
+    ThrowCompletionOr<Value> get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true);
 
 private:
     ArrayBuffer(ByteBuffer buffer, Object& prototype);
@@ -274,16 +274,15 @@ void ArrayBuffer::set_value(size_t byte_index, Value value, [[maybe_unused]] boo
 
 // 25.1.2.13 GetModifySetValueInBuffer ( arrayBuffer, byteIndex, type, value, op [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-getmodifysetvalueinbuffer
 template<typename T>
-Value ArrayBuffer::get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian)
+ThrowCompletionOr<Value> ArrayBuffer::get_modify_set_value(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian)
 {
     auto& vm = this->vm();
 
-    auto raw_bytes = numeric_to_raw_bytes<T>(vm, value, is_little_endian).release_allocated_value_but_fixme_should_propagate_errors();
+    auto raw_bytes = MUST_OR_THROW_OOM(numeric_to_raw_bytes<T>(vm, value, is_little_endian));
 
     // FIXME: Check for shared buffer
 
-    // FIXME: Propagate errors.
-    auto raw_bytes_read = MUST(buffer_impl().slice(byte_index, sizeof(T)));
+    auto raw_bytes_read = TRY_OR_THROW_OOM(vm, buffer_impl().slice(byte_index, sizeof(T)));
     auto raw_bytes_modified = operation(raw_bytes_read, raw_bytes);
     raw_bytes_modified.span().copy_to(buffer_impl().span().slice(byte_index));
 
diff --git a/Userland/Libraries/LibJS/Runtime/TypedArray.h b/Userland/Libraries/LibJS/Runtime/TypedArray.h
index bae9568ea9..9de8df1dbe 100644
--- a/Userland/Libraries/LibJS/Runtime/TypedArray.h
+++ b/Userland/Libraries/LibJS/Runtime/TypedArray.h
@@ -58,7 +58,7 @@ public:
     // 25.1.2.12 SetValueInBuffer ( arrayBuffer, byteIndex, type, value, isTypedArray, order [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-setvalueinbuffer
     virtual void set_value_in_buffer(size_t byte_index, Value, ArrayBuffer::Order, bool is_little_endian = true) = 0;
     // 25.1.2.13 GetModifySetValueInBuffer ( arrayBuffer, byteIndex, type, value, op [ , isLittleEndian ] ), https://tc39.es/ecma262/#sec-getmodifysetvalueinbuffer
-    virtual Value get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) = 0;
+    virtual ThrowCompletionOr<Value> get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) = 0;
 
 protected:
     TypedArrayBase(Object& prototype, IntrinsicConstructor intrinsic_constructor)
@@ -439,7 +439,7 @@ public:
 
     Value get_value_from_buffer(size_t byte_index, ArrayBuffer::Order order, bool is_little_endian = true) const override { return viewed_array_buffer()->template get_value<T>(byte_index, true, order, is_little_endian); }
     void set_value_in_buffer(size_t byte_index, Value value, ArrayBuffer::Order order, bool is_little_endian = true) override { viewed_array_buffer()->template set_value<T>(byte_index, value, true, order, is_little_endian); }
-    Value get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) override { return viewed_array_buffer()->template get_modify_set_value<T>(byte_index, value, move(operation), is_little_endian); }
+    ThrowCompletionOr<Value> get_modify_set_value_in_buffer(size_t byte_index, Value value, ReadWriteModifyFunction operation, bool is_little_endian = true) override { return viewed_array_buffer()->template get_modify_set_value<T>(byte_index, value, move(operation), is_little_endian); }
 
 protected:
     TypedArray(Object& prototype, IntrinsicConstructor intrinsic_constructor, u32 array_length, ArrayBuffer& array_buffer)