diff --git a/ChangeLog.adoc b/ChangeLog.adoc
index 62794c58e..d91d8d52d 100644
--- a/ChangeLog.adoc
+++ b/ChangeLog.adoc
@@ -31,6 +31,7 @@ New features::
   * core: add option `-s` in command `/command` to execute multiple commands separated by semicolons
   * core: allow case insensitive search of partial buffer name with `(?i)name` in command `/buffer`
   * core: use function util_strftimeval in evaluation of expression `date:xxx`
+  * api: return `-1` or `1` if one input string is NULL and not the other in string comparison functions
   * api: allow search by group and nick id in functions nicklist_search_group and nicklist_search_nick (issue #2081)
   * api: allow search by buffer id in function buffer_search (issue #2081)
   * api: add modifier "color_decode" to decode WeeChat colors with a replacement string
diff --git a/src/core/core-string.c b/src/core/core-string.c
index 8e9917b96..2c46e1d33 100644
--- a/src/core/core-string.c
+++ b/src/core/core-string.c
@@ -621,6 +621,12 @@ string_strcmp (const char *string1, const char *string2)
 {
     int diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     while (string1 && string1[0] && string2 && string2[0])
     {
         diff = string_charcmp (string1, string2);
@@ -649,6 +655,12 @@ string_strncmp (const char *string1, const char *string2, int max)
 {
     int count, diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     count = 0;
     while ((count < max) && string1 && string1[0] && string2 && string2[0])
     {
@@ -683,6 +695,12 @@ string_strcasecmp (const char *string1, const char *string2)
 {
     int diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     while (string1 && string1[0] && string2 && string2[0])
     {
         diff = string_charcasecmp (string1, string2);
@@ -721,6 +739,12 @@ string_strcasecmp_range (const char *string1, const char *string2, int range)
 {
     int diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     while (string1 && string1[0] && string2 && string2[0])
     {
         diff = string_charcasecmp_range (string1, string2, range);
@@ -750,6 +774,12 @@ string_strncasecmp (const char *string1, const char *string2, int max)
 {
     int count, diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     count = 0;
     while ((count < max) && string1 && string1[0] && string2 && string2[0])
     {
@@ -794,6 +824,12 @@ string_strncasecmp_range (const char *string1, const char *string2, int max,
 {
     int count, diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     count = 0;
     while ((count < max) && string1 && string1[0] && string2 && string2[0])
     {
@@ -830,6 +866,12 @@ string_strcmp_ignore_chars (const char *string1, const char *string2,
 {
     int diff;
 
+    if (!string1 && string2)
+        return -1;
+
+    if (string1 && !string2)
+        return 1;
+
     while (string1 && string1[0] && string2 && string2[0])
     {
         /* skip ignored chars */
diff --git a/tests/unit/core/test-core-string.cpp b/tests/unit/core/test-core-string.cpp
index 73750c0ab..fe4c2eccd 100644
--- a/tests/unit/core/test-core-string.cpp
+++ b/tests/unit/core/test-core-string.cpp
@@ -607,8 +607,12 @@ TEST(CoreString, StringComparison)
 {
     /* case-sensitive comparison */
     LONGS_EQUAL(0, string_strcmp (NULL, NULL));
-    LONGS_EQUAL(-97, string_strcmp (NULL, "abc"));
-    LONGS_EQUAL(97, string_strcmp ("abc", NULL));
+    LONGS_EQUAL(-1, string_strcmp (NULL, ""));
+    LONGS_EQUAL(1, string_strcmp ("", NULL));
+    LONGS_EQUAL(-1, string_strcmp (NULL, "abc"));
+    LONGS_EQUAL(1, string_strcmp ("abc", NULL));
+    LONGS_EQUAL(-97, string_strcmp ("", "abc"));
+    LONGS_EQUAL(97, string_strcmp ("abc", ""));
     LONGS_EQUAL(-98, string_strcmp ("", "b"));
     LONGS_EQUAL(98, string_strcmp ("b", ""));
     LONGS_EQUAL(0, string_strcmp ("abc", "abc"));
@@ -627,8 +631,12 @@ TEST(CoreString, StringComparison)
 
     /* case-sensitive comparison with max length */
     LONGS_EQUAL(0, string_strncmp (NULL, NULL, 3));
-    LONGS_EQUAL(-97, string_strncmp (NULL, "abc", 3));
-    LONGS_EQUAL(97, string_strncmp ("abc", NULL, 3));
+    LONGS_EQUAL(-1, string_strncmp (NULL, "", 3));
+    LONGS_EQUAL(1, string_strncmp ("", NULL, 3));
+    LONGS_EQUAL(-1, string_strncmp (NULL, "abc", 3));
+    LONGS_EQUAL(1, string_strncmp ("abc", NULL, 3));
+    LONGS_EQUAL(-97, string_strncmp ("", "abc", 3));
+    LONGS_EQUAL(97, string_strncmp ("abc", "", 3));
     LONGS_EQUAL(-98, string_strncmp ("", "b", 3));
     LONGS_EQUAL(98, string_strncmp ("b", "", 3));
     LONGS_EQUAL(0, string_strncmp ("abc", "abc", 3));
@@ -653,8 +661,12 @@ TEST(CoreString, StringComparison)
 
     /* case-insensitive comparison */
     LONGS_EQUAL(0, string_strcasecmp (NULL, NULL));
-    LONGS_EQUAL(-97, string_strcasecmp (NULL, "abc"));
-    LONGS_EQUAL(97, string_strcasecmp ("abc", NULL));
+    LONGS_EQUAL(-1, string_strcasecmp (NULL, ""));
+    LONGS_EQUAL(1, string_strcasecmp ("", NULL));
+    LONGS_EQUAL(-1, string_strcasecmp (NULL, "abc"));
+    LONGS_EQUAL(1, string_strcasecmp ("abc", NULL));
+    LONGS_EQUAL(-97, string_strcasecmp ("", "abc"));
+    LONGS_EQUAL(97, string_strcasecmp ("abc", ""));
     LONGS_EQUAL(-98, string_strcasecmp ("", "b"));
     LONGS_EQUAL(98, string_strcasecmp ("b", ""));
     LONGS_EQUAL(0, string_strcasecmp ("abc", "abc"));
@@ -673,8 +685,12 @@ TEST(CoreString, StringComparison)
 
     /* case-insensitive comparison with max length */
     LONGS_EQUAL(0, string_strncasecmp (NULL, NULL, 3));
-    LONGS_EQUAL(-97, string_strncasecmp (NULL, "abc", 3));
-    LONGS_EQUAL(97, string_strncasecmp ("abc", NULL, 3));
+    LONGS_EQUAL(-1, string_strncasecmp (NULL, "", 3));
+    LONGS_EQUAL(1, string_strncasecmp ("", NULL, 3));
+    LONGS_EQUAL(-1, string_strncasecmp (NULL, "abc", 3));
+    LONGS_EQUAL(1, string_strncasecmp ("abc", NULL, 3));
+    LONGS_EQUAL(-97, string_strncasecmp ("", "abc", 3));
+    LONGS_EQUAL(97, string_strncasecmp ("abc", "", 3));
     LONGS_EQUAL(-98, string_strncasecmp ("", "b", 3));
     LONGS_EQUAL(98, string_strncasecmp ("b", "", 3));
     LONGS_EQUAL(0, string_strncasecmp ("abc", "abc", 3));
@@ -699,8 +715,12 @@ TEST(CoreString, StringComparison)
 
     /* case-insensitive comparison with a range */
     LONGS_EQUAL(0, string_strcasecmp_range (NULL, NULL, 30));
-    LONGS_EQUAL(-97, string_strcasecmp_range (NULL, "abc", 30));
-    LONGS_EQUAL(97, string_strcasecmp_range ("abc", NULL, 30));
+    LONGS_EQUAL(-1, string_strcasecmp_range (NULL, "", 30));
+    LONGS_EQUAL(1, string_strcasecmp_range ("", NULL, 30));
+    LONGS_EQUAL(-1, string_strcasecmp_range (NULL, "abc", 30));
+    LONGS_EQUAL(1, string_strcasecmp_range ("abc", NULL, 30));
+    LONGS_EQUAL(-97, string_strcasecmp_range ("", "abc", 30));
+    LONGS_EQUAL(97, string_strcasecmp_range ("abc", "", 30));
     LONGS_EQUAL(-98, string_strcasecmp_range ("", "b", 30));
     LONGS_EQUAL(98, string_strcasecmp_range ("b", "", 30));
     LONGS_EQUAL(-2, string_strcasecmp_range ("A", "C", 30));
@@ -727,8 +747,12 @@ TEST(CoreString, StringComparison)
 
     /* case-insensitive comparison with max length and a range */
     LONGS_EQUAL(0, string_strncasecmp_range (NULL, NULL, 3, 30));
-    LONGS_EQUAL(-97, string_strncasecmp_range (NULL, "abc", 3, 30));
-    LONGS_EQUAL(97, string_strncasecmp_range ("abc", NULL, 3, 30));
+    LONGS_EQUAL(-1, string_strncasecmp_range (NULL, "", 3, 30));
+    LONGS_EQUAL(1, string_strncasecmp_range ("", NULL, 3, 30));
+    LONGS_EQUAL(-1, string_strncasecmp_range (NULL, "abc", 3, 30));
+    LONGS_EQUAL(1, string_strncasecmp_range ("abc", NULL, 3, 30));
+    LONGS_EQUAL(-97, string_strncasecmp_range ("", "abc", 3, 30));
+    LONGS_EQUAL(97, string_strncasecmp_range ("abc", "", 3, 30));
     LONGS_EQUAL(-98, string_strncasecmp_range ("", "b", 3, 30));
     LONGS_EQUAL(98, string_strncasecmp_range ("b", "", 3, 30));
     LONGS_EQUAL(-2, string_strncasecmp_range ("ABC", "CCC", 3, 30));
@@ -761,8 +785,12 @@ TEST(CoreString, StringComparison)
 
     /* comparison with chars ignored */
     LONGS_EQUAL(0, string_strcmp_ignore_chars (NULL, NULL, "", 0));
-    LONGS_EQUAL(-97, string_strcmp_ignore_chars (NULL, "abc", "", 0));
-    LONGS_EQUAL(97, string_strcmp_ignore_chars ("abc", NULL, "", 0));
+    LONGS_EQUAL(-1, string_strcmp_ignore_chars (NULL, "", "", 0));
+    LONGS_EQUAL(1, string_strcmp_ignore_chars ("", NULL, "", 0));
+    LONGS_EQUAL(-1, string_strcmp_ignore_chars (NULL, "abc", "", 0));
+    LONGS_EQUAL(1, string_strcmp_ignore_chars ("abc", NULL, "", 0));
+    LONGS_EQUAL(-97, string_strcmp_ignore_chars ("", "abc", "", 0));
+    LONGS_EQUAL(97, string_strcmp_ignore_chars ("abc", "", "", 0));
     LONGS_EQUAL(-98, string_strcmp_ignore_chars ("", "b", "", 0));
     LONGS_EQUAL(98, string_strcmp_ignore_chars ("b", "", "", 0));
     LONGS_EQUAL(-2, string_strcmp_ignore_chars ("ABC", "CCC", "", 0));