diff --git a/include/tins/ip.h b/include/tins/ip.h
index c147357..72b25ff 100644
--- a/include/tins/ip.h
+++ b/include/tins/ip.h
@@ -48,6 +48,13 @@ namespace Tins {
      * By default, IP PDUs are initialized, setting TTL to IP::DEFAULT_TTL,
      * id field to 1 and version to 4. Taking this into account, users
      * should set destination and source port and would be enough to send one.
+     *
+     * When IP is the lowest layer on a packet, and the packet is serialized
+     * this willc heck if the source address is different than 0.0.0.0. If it is,
+     * the address of the interface in which the packet is going to be sent
+     * is retrieved (by using the routing table and the destination address)
+     * and set as the source address. If you don't want this behaviour, simply
+     * set the source address to 0.0.0.0.
      */
     class IP : public PDU {
     public:
diff --git a/src/ip.cpp b/src/ip.cpp
index 1cbb360..2aa8cdd 100644
--- a/src/ip.cpp
+++ b/src/ip.cpp
@@ -426,13 +426,11 @@ void IP::write_serialization(uint8_t *buffer, uint32_t total_sz, const PDU* pare
     }
     memset(buffer + sizeof(_ip) + _options_size, 0, _padded_options_size - _options_size);
 
-    if(parent) {
-        uint32_t check = Utils::do_checksum(buffer, buffer + sizeof(_ip) + _padded_options_size);
-        while (check >> 16)
-            check = (check & 0xffff) + (check >> 16);
-        checksum(~check);
-        ((iphdr*)buffer)->check = _ip.check;
-    }
+    uint32_t check = Utils::do_checksum(buffer, buffer + sizeof(_ip) + _padded_options_size);
+    while (check >> 16)
+        check = (check & 0xffff) + (check >> 16);
+    checksum(~check);
+    ((iphdr*)buffer)->check = _ip.check;
 }
 
 bool IP::matches_response(const uint8_t *ptr, uint32_t total_sz) const {
diff --git a/tests/src/ip.cpp b/tests/src/ip.cpp
index f41e7ee..2f82b4f 100644
--- a/tests/src/ip.cpp
+++ b/tests/src/ip.cpp
@@ -26,6 +26,7 @@ public:
         fragmented_ether_ip_packet[], tot_len_zero_packet[];
     
     void test_equals(const IP &ip1, const IP &ip2);
+    void test_overwrite_source_address(IP& ip);
 };
 
 const uint8_t IPTest::expected_packet[] = { 
@@ -718,3 +719,42 @@ TEST_F(IPTest, RemoveOption) {
     PDU::serialization_type new_buffer = ip.serialize();
     EXPECT_EQ(old_buffer, new_buffer);
 }
+
+void IPTest::test_overwrite_source_address(IP& ip) {
+    const uint8_t expected_output[] = {
+        69,0,0,40,0,1,0,0,128,6,38,186,1,2,3,4,8,8,8,8,0,32,0,12,0,
+        0,0,0,0,0,0,0,80,0,127,166,27,253,0,0
+    };
+    // Add TCP so we can check if the timestamp is correctly calculated
+    ip /= TCP(12, 32);
+
+    PDU::serialization_type buffer = ip.serialize();
+    EXPECT_EQ(IPv4Address("1.2.3.4"), ip.src_addr());
+    EXPECT_EQ(0x26ba, ip.checksum());
+
+    vector<uint8_t> output_buffer(expected_output, 
+                                  expected_output + sizeof(expected_output));
+    EXPECT_EQ(output_buffer, buffer);
+}
+
+TEST_F(IPTest, OverwriteSourceAddress) {
+    IP ip("8.8.8.8");
+    ip.src_addr("1.2.3.4");
+    test_overwrite_source_address(ip);
+}
+
+TEST_F(IPTest, OverwriteSourceAddressUsingConstructor) {
+    IP ip("8.8.8.8", "1.2.3.4");
+    test_overwrite_source_address(ip);
+}
+
+TEST_F(IPTest, OverwriteSourceAddressConstructingFromBuffer) {
+    // Only the expected packet's IP layer
+    const uint8_t expected_output[] = {
+        69,0,0,20,0,1,0,0,128,0,0,0,1,2,3,4,8,8,8,8
+    };
+    IP ip(expected_output, sizeof(expected_output));
+    test_overwrite_source_address(ip);
+}
+
+