diff --git a/src/gmio_stl/stlb_header.h b/src/gmio_stl/stlb_header.h
index 2eaa164..ee3cc3d 100644
--- a/src/gmio_stl/stlb_header.h
+++ b/src/gmio_stl/stlb_header.h
@@ -47,7 +47,7 @@ struct gmio_stlb_header gmio_stlb_header_str(const char* str);
 /*! Copies \p header into C string \p str
  *
  *  It replaces non-printable bytes with \p replacement char.
- *  \p str must be at least \c GMIO_STLB_HEADER_SIZE long, a terminating null
+ *  \p str must be at least \c GMIO_STLB_HEADER_SIZE+1 long, a terminating null
  *  character ('\0') is copied at position \c GMIO_STLB_HEADER_SIZE
  */
 GMIO_LIBSTL_EXPORT
diff --git a/tests/CMakeLists.txt b/tests/CMakeLists.txt
index 1597e00..6eed3cc 100644
--- a/tests/CMakeLists.txt
+++ b/tests/CMakeLists.txt
@@ -55,6 +55,7 @@ set(GMIO_TEST_STL_SRC
         test_stl_internal.c
         test_stl_io.c
         test_stl_infos.c
+        test_stlb_header.c
         core_utils.c
         stl_utils.c)
 if(GMIO_BUILD_SHARED_LIBS)
diff --git a/tests/main_test_stl.c b/tests/main_test_stl.c
index d82daaf..0b6f7ae 100644
--- a/tests/main_test_stl.c
+++ b/tests/main_test_stl.c
@@ -18,11 +18,15 @@
 const char* test_stl_internal__rw_common();
 
 const char* test_stl_infos();
+
 const char* test_stl_read();
 const char* test_stla_write();
 const char* test_stlb_write_header();
 const char* test_stlb_write();
 
+const char* test_stlb_header_str();
+const char* test_stlb_header_to_printable_str();
+
 const char* all_tests()
 {
     UTEST_SUITE_START();
@@ -34,6 +38,8 @@ const char* all_tests()
     UTEST_RUN(test_stla_write);
     UTEST_RUN(test_stlb_write_header);
     UTEST_RUN(test_stlb_write);
+    UTEST_RUN(test_stlb_header_str);
+    UTEST_RUN(test_stlb_header_to_printable_str);
 
     return NULL;
 }
diff --git a/tests/test_stlb_header.c b/tests/test_stlb_header.c
new file mode 100644
index 0000000..d833ba9
--- /dev/null
+++ b/tests/test_stlb_header.c
@@ -0,0 +1,81 @@
+/****************************************************************************
+** gmio
+** Copyright Fougue (2 Mar. 2015)
+** contact@fougue.pro
+**
+** This software is a reusable library whose purpose is to provide complete
+** I/O support for various CAD file formats (eg. STL)
+**
+** This software is governed by the CeCILL-B license under French law and
+** abiding by the rules of distribution of free software.  You can  use,
+** modify and/ or redistribute the software under the terms of the CeCILL-B
+** license as circulated by CEA, CNRS and INRIA at the following URL
+** "http://www.cecill.info/licences/Licence_CeCILL-B_V1-en.html".
+****************************************************************************/
+
+#include "utest_assert.h"
+
+#include "../src/gmio_stl/stlb_header.h"
+
+#include <string.h>
+
+const char* test_stlb_header_str()
+{
+    const struct gmio_stlb_header null = {0};
+
+    {
+        const struct gmio_stlb_header h = gmio_stlb_header_str("");
+        UTEST_ASSERT(memcmp(&h, &null, GMIO_STLB_HEADER_SIZE) == 0);
+    }
+
+    {
+        const char cstr[] = "gmio by Fougue";
+        const struct gmio_stlb_header h = gmio_stlb_header_str(cstr);
+        UTEST_COMPARE_CSTR((const char*)h.data, cstr);
+        UTEST_ASSERT(memcmp(
+                         &h.data[sizeof(cstr)],
+                         &null.data[sizeof(cstr)],
+                         GMIO_STLB_HEADER_SIZE - sizeof(cstr))
+                     == 0);
+    }
+
+    {
+        const char cstr[] = { /* size = 104(26*4) */
+            "abcdefghijklmnopqrstuvwxyz"
+            "abcdefghijklmnopqrstuvwxyz"
+            "abcdefghijklmnopqrstuvwxyz"
+            "abcdefghijklmnopqrstuvwxyz"
+        };
+        const struct gmio_stlb_header h = gmio_stlb_header_str(cstr);
+        UTEST_ASSERT(strncmp((const char*)h.data, cstr, GMIO_STLB_HEADER_SIZE)
+                     == 0);
+    }
+
+    return NULL;
+}
+
+const char* test_stlb_header_to_printable_str()
+{
+    {
+        const struct gmio_stlb_header null = {0};
+        char cstr[GMIO_STLB_HEADER_SIZE+1];
+        gmio_stlb_header_to_printable_str(&null, cstr, 0);
+        UTEST_ASSERT(memcmp(&cstr, &null, GMIO_STLB_HEADER_SIZE) == 0);
+        UTEST_COMPARE_UINT(strlen(cstr), 0);
+    }
+
+    {
+        char cstr[GMIO_STLB_HEADER_SIZE+1];
+        const char cstr_ab[] = "abcdefghijklmnopqrstuvwxyz";
+        const char cstr_ab_after_cpy[] = "abcde?ghijklmnopqrstuvwxyz";
+        struct gmio_stlb_header h = gmio_stlb_header_str(cstr_ab);
+        h.data[5] = 7; /* Bell */
+        gmio_stlb_header_to_printable_str(&h, cstr, '?');
+        UTEST_ASSERT(strncmp(cstr_ab_after_cpy,
+                             cstr,
+                             sizeof(cstr_ab_after_cpy) - 1)
+                     == 0);
+    }
+
+    return NULL;
+}