diff --git a/include/tins/detail/sequence_number_helpers.h b/include/tins/detail/sequence_number_helpers.h
new file mode 100644
index 0000000..04af18d
--- /dev/null
+++ b/include/tins/detail/sequence_number_helpers.h
@@ -0,0 +1,49 @@
+/*
+ * Copyright (c) 2017, Matias Fontanini
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions are
+ * met:
+ *
+ * * Redistributions of source code must retain the above copyright
+ *   notice, this list of conditions and the following disclaimer.
+ * * Redistributions in binary form must reproduce the above
+ *   copyright notice, this list of conditions and the following disclaimer
+ *   in the documentation and/or other materials provided with the
+ *   distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
+ * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
+ * OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+ * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+ * LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
+ * OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ *
+ */
+
+#ifndef TINS_SEQUENCE_NUMBER_HELPERS_H
+#define TINS_SEQUENCE_NUMBER_HELPERS_H
+
+#include <stdint.h>
+/**
+ * \cond
+ */
+namespace Tins {
+namespace Internals {
+
+// Compares sequence numbers as defined by RFC 1982.
+int seq_compare(uint32_t seq1, uint32_t seq2);
+
+} // namespace Internals
+} // namespace Tins
+/**
+ * \endcond
+ */
+
+#endif // TINS_SEQUENCE_NUMBER_HELPERS_H
diff --git a/include/tins/internals.h b/include/tins/internals.h
index 9de7866..e44d30c 100644
--- a/include/tins/internals.h
+++ b/include/tins/internals.h
@@ -30,26 +30,11 @@
 #ifndef TINS_INTERNALS_H
 #define TINS_INTERNALS_H
 
-#include <stdint.h>
 #include "detail/type_traits.h"
 #include "detail/address_helpers.h"
 #include "detail/icmp_extension_helpers.h"
 #include "detail/smart_ptr.h"
 #include "detail/pdu_helpers.h"
-
-/**
- * \cond
- */
-namespace Tins {
-namespace Internals {
-
-// Compares sequence numbers as defined by RFC 1982.
-int seq_compare(uint32_t seq1, uint32_t seq2);
-
-} // namespace Internals
-} // namespace Tins
-/**
- * \endcond
- */
+#include "detail/sequence_number_helpers.h"
 
 #endif
diff --git a/src/CMakeLists.txt b/src/CMakeLists.txt
index 58e4920..9fff026 100644
--- a/src/CMakeLists.txt
+++ b/src/CMakeLists.txt
@@ -24,6 +24,7 @@ set(SOURCES
     detail/address_helpers.cpp
     detail/icmp_extension_helpers.cpp
     detail/pdu_helpers.cpp
+    detail/sequence_number_helpers.cpp
     dhcp.cpp
     dhcpv6.cpp
     dns.cpp
@@ -35,7 +36,6 @@ set(SOURCES
     icmp_extension.cpp
     icmp.cpp
     icmpv6.cpp
-    internals.cpp
     ip_reassembler.cpp
     ip.cpp
     ip_address.cpp
diff --git a/src/internals.cpp b/src/detail/sequence_number_helpers.cpp
similarity index 96%
rename from src/internals.cpp
rename to src/detail/sequence_number_helpers.cpp
index 78c63fb..7c8acec 100644
--- a/src/internals.cpp
+++ b/src/detail/sequence_number_helpers.cpp
@@ -27,7 +27,7 @@
  *
  */
 
-#include "internals.h"
+#include "detail/sequence_number_helpers.h"
 
 namespace Tins {
 namespace Internals {
@@ -46,5 +46,5 @@ int seq_compare(uint32_t seq1, uint32_t seq2) {
     }
 }
 
-} // namespace Internals
-} // namespace Tins
+} // Internals
+} // Tins
diff --git a/src/tcp_ip/ack_tracker.cpp b/src/tcp_ip/ack_tracker.cpp
index 101a28e..a4129d2 100644
--- a/src/tcp_ip/ack_tracker.cpp
+++ b/src/tcp_ip/ack_tracker.cpp
@@ -33,7 +33,7 @@
 
 #include <limits>
 #include "tcp.h"
-#include "internals.h"
+#include "detail/sequence_number_helpers.h"
 
 using std::vector;
 using std::numeric_limits;
diff --git a/src/tcp_ip/data_tracker.cpp b/src/tcp_ip/data_tracker.cpp
index 9256de2..0987513 100644
--- a/src/tcp_ip/data_tracker.cpp
+++ b/src/tcp_ip/data_tracker.cpp
@@ -31,7 +31,7 @@
 
 #ifdef TINS_HAVE_TCPIP
 
-#include "internals.h"
+#include "detail/sequence_number_helpers.h"
 
 using std::move;
 
diff --git a/src/tcp_ip/flow.cpp b/src/tcp_ip/flow.cpp
index 0742d56..64e09db 100644
--- a/src/tcp_ip/flow.cpp
+++ b/src/tcp_ip/flow.cpp
@@ -40,7 +40,7 @@
 #include "ip.h"
 #include "ipv6.h"
 #include "rawpdu.h"
-#include "internals.h"
+#include "detail/sequence_number_helpers.h"
 #include "exceptions.h"
 #include "memory_helpers.h"