diff --git a/src/cmdline.c b/src/cmdline.c
index 5f390a7..1f94a67 100644
--- a/src/cmdline.c
+++ b/src/cmdline.c
@@ -462,7 +462,7 @@ static int tab_handling(opt_t *result, char *optarg)
     char *p;
     int width = (int) strtol(optarg, &p, 10);
     if (width < 1 || width > MAX_TABSTOP) {
-        fprintf(stderr, "%s: invalid tab stop distance -- %d\n", PROJECT, width);
+        bx_fprintf(stderr, "%s: invalid tab stop distance -- %d\n", PROJECT, width);
         return 1;
     }
     result->tabstop = width;
@@ -490,7 +490,7 @@ static int tab_handling(opt_t *result, char *optarg)
         }
     }
     if (errfl) {
-        fprintf(stderr, "%s: invalid tab handling specification - %s\n", PROJECT, optarg);
+        bx_fprintf(stderr, "%s: invalid tab handling specification - %s\n", PROJECT, optarg);
         return 1;
     }
     return 0;
diff --git a/utest/cmdline_test.c b/utest/cmdline_test.c
index 7d15792..a8aa3b8 100644
--- a/utest/cmdline_test.c
+++ b/utest/cmdline_test.c
@@ -235,4 +235,76 @@ void test_padding_novalue(void **state)
 }
 
 
+void test_tabstops_zero(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "0");
+
+    assert_null(actual);   // invalid option, so we would need to exit with error
+    assert_int_equal(1, collect_err_size);
+    assert_string_equal("boxes: invalid tab stop distance -- 0\n", collect_err[0]);
+}
+
+
+void test_tabstops_500(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "500");
+
+    assert_null(actual);   // invalid option, so we would need to exit with error
+    assert_int_equal(1, collect_err_size);
+    assert_string_equal("boxes: invalid tab stop distance -- 500\n", collect_err[0]);
+}
+
+
+void test_tabstops_4X(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "4X");
+
+    assert_null(actual);   // invalid option, so we would need to exit with error
+    assert_int_equal(1, collect_err_size);
+    assert_string_equal("boxes: invalid tab handling specification - 4X\n", collect_err[0]);
+}
+
+
+void test_tabstops_4e(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "4e");
+
+    assert_non_null(actual);
+    assert_int_equal(4, actual->tabstop);
+    assert_int_equal((int) 'e', (int) actual->tabexp);
+}
+
+
+void test_tabstops_4ex(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "4ex");
+
+    assert_null(actual);   // invalid option, so we would need to exit with error
+    assert_int_equal(1, collect_err_size);
+    assert_string_equal("boxes: invalid tab handling specification - 4ex\n", collect_err[0]);
+}
+
+
+void test_tabstops_7(void **state)
+{
+    (void) state;  /* unused */
+
+    opt_t *actual = act(2, "-t", "7");
+
+    assert_non_null(actual);
+    assert_int_equal(7, actual->tabstop);
+    assert_int_equal((int) 'e', (int) actual->tabexp);
+}
+
+
 /*EOF*/                                          /* vim: set cindent sw=4: */
diff --git a/utest/cmdline_test.h b/utest/cmdline_test.h
index e7795bd..7b5b54c 100644
--- a/utest/cmdline_test.h
+++ b/utest/cmdline_test.h
@@ -44,6 +44,13 @@ void test_padding_notset(void **state);
 void test_padding_invalid_value(void **state);
 void test_padding_novalue(void **state);
 
+void test_tabstops_zero(void **state);
+void test_tabstops_500(void **state);
+void test_tabstops_4X(void **state);
+void test_tabstops_4e(void **state);
+void test_tabstops_4ex(void **state);
+void test_tabstops_7(void **state);
+
 
 #endif
 
diff --git a/utest/main.c b/utest/main.c
index ef025e6..0110565 100644
--- a/utest/main.c
+++ b/utest/main.c
@@ -62,7 +62,13 @@ int main(void)
         cmocka_unit_test_setup(test_padding_negative, beforeTest),
         cmocka_unit_test_setup(test_padding_notset, beforeTest),
         cmocka_unit_test_setup(test_padding_invalid_value, beforeTest),
-        cmocka_unit_test_setup(test_padding_novalue, beforeTest)
+        cmocka_unit_test_setup(test_padding_novalue, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_zero, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_500, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_4X, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_4e, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_4ex, beforeTest),
+        cmocka_unit_test_setup(test_tabstops_7, beforeTest)
     };
 
     const struct CMUnitTest regulex_tests[] = {