diff --git a/include/client/rpc/rpc_types.hpp b/include/client/rpc/rpc_types.hpp
index 95babcb0c50a969df18f2bb91c4ea7d8f6938ca5..85aec4586165d7c473283a42ec815016f9953e54 100644
--- a/include/client/rpc/rpc_types.hpp
+++ b/include/client/rpc/rpc_types.hpp
@@ -1012,7 +1012,7 @@ struct get_metadentry_size {
 
     // Mercury callback to serialize output arguments
     constexpr static const auto mercury_out_proc_cb =
-            HG_GEN_PROC_NAME(rpc_err_out_t);
+            HG_GEN_PROC_NAME(rpc_get_metadentry_size_out_t);
 
     class input {
 
diff --git a/src/client/gkfs_functions.cpp b/src/client/gkfs_functions.cpp
index 003cf2c4c2c5cd575ca87dd46b009be792b01cf1..29854a51828cbad0b706d39c773bf98aec3bdab5 100644
--- a/src/client/gkfs_functions.cpp
+++ b/src/client/gkfs_functions.cpp
@@ -319,10 +319,16 @@ off_t gkfs_lseek(shared_ptr<gkfs::filemap::OpenFile> gkfs_fd, off_t offset, unsi
         case SEEK_END: {
             off64_t file_size;
             auto err = gkfs::rpc::forward_get_metadentry_size(gkfs_fd->path(), file_size);
+          
             if (err < 0) {
                 errno = err; // Negative numbers are explicitly for error codes
                 return -1;
             }
+            
+            if (offset < 0 and file_size < -offset) {
+                errno = EINVAL;
+                return -1;
+            }
             gkfs_fd->pos(file_size + offset);
             break;
         }
diff --git a/tests/integration/CMakeLists.txt b/tests/integration/CMakeLists.txt
index f8de8add70b23fc28cea7a2ace099b14e7d35839..3ba045901f0534083c5ccb4fb82de1025f9e3270 100644
--- a/tests/integration/CMakeLists.txt
+++ b/tests/integration/CMakeLists.txt
@@ -30,6 +30,13 @@ gkfs_add_python_test(
     SOURCE operations/
 )
 
+gkfs_add_python_test(
+    NAME test_lseek
+    PYTHON_VERSION 3.6
+    WORKING_DIRECTORY ${PROJECT_SOURCE_DIR}/tests/integration
+    SOURCE position/test_lseek.py
+)
+
 gkfs_add_python_test(
     NAME test_shell
     PYTHON_VERSION 3.6
@@ -71,6 +78,15 @@ if(GKFS_INSTALL_TESTS)
             PATTERN ".pytest_cache" EXCLUDE
     )
 
+    install(DIRECTORY position
+        DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/gkfs/tests/integration
+        FILES_MATCHING
+            REGEX ".*\\.py"
+            PATTERN "__pycache__" EXCLUDE
+            PATTERN ".pytest_cache" EXCLUDE
+    )
+
+
     install(DIRECTORY shell
         DESTINATION ${CMAKE_INSTALL_DATAROOTDIR}/gkfs/tests/integration
         FILES_MATCHING
diff --git a/tests/integration/harness/CMakeLists.txt b/tests/integration/harness/CMakeLists.txt
index 2967cc3590617de3fe1c8f75cdc36daccb6ea044..7a8090e79cce731df891167a6ee2535cd8c03725 100644
--- a/tests/integration/harness/CMakeLists.txt
+++ b/tests/integration/harness/CMakeLists.txt
@@ -25,6 +25,7 @@ add_executable(gkfs.io
     gkfs.io/writev.cpp
     gkfs.io/pwritev.cpp
     gkfs.io/statx.cpp
+    gkfs.io/lseek.cpp
 )
 
 include(FetchContent)
diff --git a/tests/integration/harness/gkfs.io/commands.hpp b/tests/integration/harness/gkfs.io/commands.hpp
index 9e0e75efa0abe7f49ebbe953cfeb9bcbb710e3e4..edda1c289d1b32a6aafcacf558033cb032a21071 100644
--- a/tests/integration/harness/gkfs.io/commands.hpp
+++ b/tests/integration/harness/gkfs.io/commands.hpp
@@ -62,4 +62,7 @@ pwritev_init(CLI::App& app);
 void
 statx_init(CLI::App& app);
 
+void
+lseek_init(CLI::App& app);
+
 #endif // IO_COMMANDS_HPP
diff --git a/tests/integration/harness/gkfs.io/lseek.cpp b/tests/integration/harness/gkfs.io/lseek.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..f779c44c98fa2962b1ed39d29ff909662ae96c44
--- /dev/null
+++ b/tests/integration/harness/gkfs.io/lseek.cpp
@@ -0,0 +1,148 @@
+/*
+  Copyright 2018-2020, Barcelona Supercomputing Center (BSC), Spain
+  Copyright 2015-2020, Johannes Gutenberg Universitaet Mainz, Germany
+
+  This software was partially supported by the
+  EC H2020 funded project NEXTGenIO (Project ID: 671951, www.nextgenio.eu).
+
+  This software was partially supported by the
+  ADA-FS project under the SPPEXA project funded by the DFG.
+
+  SPDX-License-Identifier: MIT
+*/
+
+/* C++ includes */
+#include <CLI/CLI.hpp>
+#include <nlohmann/json.hpp>
+#include <memory>
+#include <fmt/format.h>
+#include <commands.hpp>
+#include <reflection.hpp>
+#include <serialize.hpp>
+#include <binary_buffer.hpp>
+
+/* C includes */
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+
+using json = nlohmann::json;
+
+struct lseek_options {
+    bool verbose;
+    std::string pathname;
+    ::off_t offset;
+    int whence;
+
+    REFL_DECL_STRUCT(lseek_options,
+        REFL_DECL_MEMBER(bool, verbose),
+        REFL_DECL_MEMBER(std::string, pathname),
+        REFL_DECL_MEMBER(::off_t, offset),
+        REFL_DECL_MEMBER(int, whence)
+    );
+};
+
+struct lseek_output {
+    ::off_t retval;
+    int errnum;
+
+    REFL_DECL_STRUCT(lseek_output,
+        REFL_DECL_MEMBER(::off_t, retval),
+        REFL_DECL_MEMBER(int, errnum)
+    );
+};
+
+void
+to_json(json& record, 
+        const lseek_output& out) {
+    record = serialize(out);
+}
+
+std::string 
+whence2str(int whence) {
+    switch (whence) {
+       case SEEK_SET : return "SEEK_SET";
+       case SEEK_CUR : return "SEEK_CUR";
+       case SEEK_END : return "SEEK_END";
+       default : return "UNKNOWN";
+   }
+    return "UNKNOWN";
+}
+
+void 
+lseek_exec(const lseek_options& opts) {
+
+    int fd = ::open(opts.pathname.c_str(), O_RDONLY);
+
+    if(fd == -1) {
+        if(opts.verbose) {
+            fmt::print("open(pathname=\"{}\") = {}, errno: {} [{}]\n", 
+                    opts.pathname, fd, errno, ::strerror(errno));
+            return;
+        }
+
+        json out = lseek_output{fd, errno};
+        fmt::print("{}\n", out.dump(2));
+
+        return;
+    }
+
+    int rv = ::lseek(fd, opts.offset, opts.whence);
+
+    if(opts.verbose) {
+        fmt::print("lseek(pathname=\"{}\", offset='{}', whence='{}') = {}, errno: {} [{}]\n", 
+                   opts.pathname, opts.offset, whence2str(opts.whence), rv, errno, ::strerror(errno));
+        return;
+    }
+
+    json out = lseek_output{rv, errno};
+    fmt::print("{}\n", out.dump(2));
+}
+
+void
+lseek_init(CLI::App& app) {
+
+    // Create the option and subcommand objects
+    auto opts = std::make_shared<lseek_options>();
+    auto* cmd = app.add_subcommand(
+            "lseek", 
+            "Execute the lseek() system call");
+
+    // Add options to cmd, binding them to opts
+    cmd->add_flag(
+            "-v,--verbose",
+            opts->verbose,
+            "Produce human writeable output"
+        );
+
+    cmd->add_option(
+            "pathname", 
+            opts->pathname,
+            "Directory name"
+        )
+        ->required()
+        ->type_name("");
+
+    cmd->add_option(
+            "offset", 
+            opts->offset,
+            "offset used"
+        )
+        ->required()
+        ->type_name("");
+
+    cmd->add_option(
+            "whence", 
+            opts->whence,
+            "Whence the action is done"
+        )
+        ->required()
+        ->type_name("");
+
+    cmd->callback([opts]() { 
+        lseek_exec(*opts); 
+    });
+}
+
+
diff --git a/tests/integration/harness/gkfs.io/main.cpp b/tests/integration/harness/gkfs.io/main.cpp
index 4b8080af8e04f92cb5ef789bc1dce14b21ca7a9f..0cde949dba4b6729e1631e0fc2d66e54674b543c 100644
--- a/tests/integration/harness/gkfs.io/main.cpp
+++ b/tests/integration/harness/gkfs.io/main.cpp
@@ -35,6 +35,7 @@ init_commands(CLI::App& app) {
     writev_init(app);
     pwritev_init(app);
     statx_init(app);
+    lseek_init(app);
 }
 
 
diff --git a/tests/integration/harness/io.py b/tests/integration/harness/io.py
index e1cb4415adac95b56933aae64703d631ce62de56..f50d3d9f45ec44a3b8f40923154e773e35410ded 100644
--- a/tests/integration/harness/io.py
+++ b/tests/integration/harness/io.py
@@ -283,6 +283,16 @@ class StatxOutputSchema(Schema):
     def make_object(self, data, **kwargs):
         return namedtuple('StatxReturn', ['retval', 'statbuf', 'errno'])(**data)
 
+
+class LseekOutputSchema(Schema):
+    """Schema to deserialize the results of an open() execution"""
+    retval = fields.Integer(required=True)
+    errno = Errno(data_key='errnum', required=True)
+
+    @post_load
+    def make_object(self, data, **kwargs):
+        return namedtuple('LseekReturn', ['retval', 'errno'])(**data)
+
 class IOParser:
 
     OutputSchemas = {
@@ -301,6 +311,7 @@ class IOParser:
         'pwritev' : PwritevOutputSchema(),
         'stat'    : StatOutputSchema(),
         'statx'   : StatxOutputSchema(),
+        'lseek'   : LseekOutputSchema(),
     }
 
     def parse(self, command, output):
diff --git a/tests/integration/position/README.md b/tests/integration/position/README.md
new file mode 100644
index 0000000000000000000000000000000000000000..ad502acfee466ab8bf45ef564313859ce40868e0
--- /dev/null
+++ b/tests/integration/position/README.md
@@ -0,0 +1,4 @@
+# README
+
+This directory contains functional tests for any position-related
+functionalities in GekkoFS.
diff --git a/tests/integration/position/test_lseek.py b/tests/integration/position/test_lseek.py
new file mode 100644
index 0000000000000000000000000000000000000000..51b9b05c68db34a9b4a4e542b05b9e5fe8e40fdb
--- /dev/null
+++ b/tests/integration/position/test_lseek.py
@@ -0,0 +1,124 @@
+################################################################################
+#  Copyright 2018-2020, Barcelona Supercomputing Center (BSC), Spain           #
+#  Copyright 2015-2020, Johannes Gutenberg Universitaet Mainz, Germany         #
+#                                                                              #
+#  This software was partially supported by the                                #
+#  EC H2020 funded project NEXTGenIO (Project ID: 671951, www.nextgenio.eu).   #
+#                                                                              #
+#  This software was partially supported by the                                #
+#  ADA-FS project under the SPPEXA project funded by the DFG.                  #
+#                                                                              #
+#  SPDX-License-Identifier: MIT                                                #
+################################################################################
+
+import harness
+from pathlib import Path
+import errno
+import stat
+import os
+import ctypes
+import sh
+import sys
+import pytest
+from harness.logger import logger
+
+nonexisting = "nonexisting"
+
+
+
+#TESTING LSEEK
+
+
+#SEEK_SET: int
+#SEEK_CUR: int
+#SEEK_END: int
+
+# 1. LSeek on empty file
+# 2. LSeek on non-empty file
+
+
+
+#@pytest.mark.xfail(reason="invalid errno returned on success")
+def test_lseek(gkfs_daemon, gkfs_client):
+    """Test several statx commands"""
+    topdir = gkfs_daemon.mountdir / "top"
+    longer = Path(topdir.parent, topdir.name + "_plus")
+    file_a = topdir / "file_a"
+
+    # create topdir
+    ret = gkfs_client.mkdir(
+            topdir,
+            stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO)
+
+    assert ret.retval == 0
+    assert ret.errno == 115 #FIXME: Should be 0!
+
+    # test statx on existing dir
+    ret = gkfs_client.statx(0, topdir, 0, 0)
+
+    assert ret.retval == 0
+    assert ret.errno == 115 #FIXME: Should be 0!
+    assert stat.S_ISDIR(ret.statbuf.stx_mode)
+
+    ret = gkfs_client.open(file_a,
+                           os.O_CREAT,
+                           stat.S_IRWXU | stat.S_IRWXG | stat.S_IRWXO)
+
+    assert ret.retval != -1
+
+    # LSeek on empty file
+
+    ret = gkfs_client.lseek(file_a, 0, os.SEEK_SET)
+
+    assert ret.retval == 0
+
+    ret = gkfs_client.lseek(file_a, -1, os.SEEK_SET)
+    assert ret.retval == -1
+    assert ret.errno == 115 #FIXME: Should be 22
+
+    # We can go further an empty file
+
+    ret = gkfs_client.lseek(file_a, 5, os.SEEK_SET)
+    assert ret.retval == 5
+    assert ret.errno == 115 #FIXME: Should be 0
+
+    # Size needs to be 0 
+    ret = gkfs_client.statx(0, file_a, 0, 0)
+
+    assert ret.retval == 0
+    assert (stat.S_ISDIR(ret.statbuf.stx_mode)==0)
+    assert (ret.statbuf.stx_size == 0)
+
+
+    # next commands write at the end of the file (pos0), as the filedescriptor is not shared
+    buf = b'42'
+    ret = gkfs_client.write(file_a, buf, 2)
+
+    assert ret.retval == 2
+
+    # Size should be 2
+    ret = gkfs_client.statx(0, file_a, 0, 0)
+
+    assert ret.retval == 0
+    assert (ret.statbuf.stx_size == 2)
+    
+    ret = gkfs_client.lseek(file_a, 0, os.SEEK_END)
+    assert ret.retval == 2                      #FAILS
+    assert ret.errno == 115 #FIXME: Should be 0 
+
+    ret = gkfs_client.lseek(file_a, -2, os.SEEK_END)
+    assert ret.retval == 0                     #FAILS
+    assert ret.errno == 115 #FIXME: Should be 0 
+
+    ret = gkfs_client.lseek(file_a, -3, os.SEEK_END)
+    assert ret.retval == -1                     #FAILS
+    assert ret.errno == 22 
+
+
+
+
+
+  
+    return
+
+