diff --git a/glib/gstring.h b/glib/gstring.h
index ef219a62a..b82123198 100644
--- a/glib/gstring.h
+++ b/glib/gstring.h
@@ -34,6 +34,7 @@
 #include <glib/gtypes.h>
 #include <glib/gunicode.h>
 #include <glib/gbytes.h>
+#include <glib/gstrfuncs.h>
 #include <glib/gutils.h>  /* for G_CAN_INLINE */
 #include <string.h>
 
@@ -182,7 +183,9 @@ g_string_append_c_inline (GString *gstring,
     g_string_insert_c (gstring, -1, c);
   return gstring;
 }
-#define g_string_append_c(gstr,c)       g_string_append_c_inline (gstr, c)
+
+#define g_string_append_c(gstr,c) \
+  g_string_append_c_inline (gstr, c)
 
 G_ALWAYS_INLINE
 static inline GString *
@@ -190,6 +193,12 @@ g_string_append_len_inline (GString    *gstring,
                             const char *val,
                             gssize      len)
 {
+  if G_UNLIKELY (gstring == NULL)
+    return g_string_append_len (gstring, val, len);
+
+  if G_UNLIKELY (val == NULL)
+    return (len != 0) ? g_string_append_len (gstring, val, len) : gstring;
+
   if (len < 0)
     len = strlen (val);
 
@@ -207,7 +216,9 @@ g_string_append_len_inline (GString    *gstring,
   else
     return g_string_insert_len (gstring, -1, val, len);
 }
-#define g_string_append_len(gstr,val,len) g_string_append_len_inline (gstr, val, len)
+
+#define g_string_append_len(gstr, val, len) \
+  g_string_append_len_inline (gstr, val, len)
 
 G_ALWAYS_INLINE
 static inline GString *
@@ -219,13 +230,24 @@ g_string_truncate_inline (GString *gstring,
   return gstring;
 }
 
-#define g_string_truncate(gstr,len) g_string_truncate_inline (gstr, len)
+#define g_string_truncate(gstr, len) \
+  g_string_truncate_inline (gstr, len)
 
 #if G_GNUC_CHECK_VERSION (2, 0)
 
-#define g_string_append(gstr,val) g_string_append_len (gstr, val, __builtin_constant_p (val) ? (gssize) strlen (val) : (gssize) -1)
+#define g_string_append(gstr, val)                  \
+  (__builtin_constant_p (val) ?                     \
+    G_GNUC_EXTENSION ({                             \
+      const char * const __val = (val);             \
+      g_string_append_len (gstr, __val,             \
+        G_LIKELY (__val != NULL) ?                  \
+          (gssize) strlen (_G_STR_NONNULL (__val))  \
+        : (gssize) -1);                             \
+    })                                              \
+    :                                               \
+    g_string_append_len (gstr, val, (gssize) -1))
 
-#endif
+#endif /* G_GNUC_CHECK_VERSION (2, 0) */
 
 #endif /* G_CAN_INLINE */
 
diff --git a/glib/tests/cxx.cpp b/glib/tests/cxx.cpp
index f7129bcf7..6e4727f2a 100644
--- a/glib/tests/cxx.cpp
+++ b/glib/tests/cxx.cpp
@@ -321,6 +321,106 @@ test_str_equal (void)
   g_free (str_b);
 }
 
+
+static void
+test_string_append (void)
+{
+  GString *string;
+  char *tmp;
+  int i;
+
+  tmp = g_strdup ("more");
+
+  /* append */
+  string = g_string_new ("firsthalf");
+  g_string_append (string, "last");
+  (g_string_append) (string, "half");
+
+  g_assert_cmpstr (string->str, ==, "firsthalflasthalf");
+
+  i = 0;
+  g_string_append (string, &tmp[i++]);
+  (g_string_append) (string, &tmp[i++]);
+  g_assert_true (i == 2);
+  g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreore");
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null (g_string_append (NULL, NULL));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null ((g_string_append) (NULL, NULL));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append (string, NULL) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append) (string, NULL) == string);
+  g_test_assert_expected_messages ();
+
+  g_string_free (string, TRUE);
+
+  /* append_len */
+  string = g_string_new ("firsthalf");
+  g_string_append_len (string, "lasthalfjunkjunk", strlen ("last"));
+  (g_string_append_len) (string, "halfjunkjunk", strlen ("half"));
+  g_string_append_len (string, "more", -1);
+  (g_string_append_len) (string, "ore", -1);
+
+  g_assert_true (g_string_append_len (string, NULL, 0) == string);
+  g_assert_true ((g_string_append_len) (string, NULL, 0) == string);
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null (g_string_append_len (NULL, NULL, -1));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null ((g_string_append_len) (NULL, NULL, -1));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append_len (string, NULL, -1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append_len) (string, NULL, -1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append_len (string, NULL, 1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append_len) (string, NULL, 1) == string);
+  g_test_assert_expected_messages ();
+
+  g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreore");
+
+  char c = 'A';
+  g_string_append_c (string, c++);
+  (g_string_append_c) (string, c++);
+  g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreoreAB");
+
+  i = string->len;
+  g_string_truncate (string, --i);
+  (g_string_truncate) (string, --i);
+  g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreore");
+
+  g_string_free (string, TRUE);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -344,6 +444,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/C++/clear-pointer", test_clear_pointer);
   g_test_add_func ("/C++/steal-pointer", test_steal_pointer);
   g_test_add_func ("/C++/str-equal", test_str_equal);
+  g_test_add_func ("/C++/string-append", test_string_append);
 
   return g_test_run ();
 }
diff --git a/glib/tests/string.c b/glib/tests/string.c
index 92138c0ba..46c3d7b8a 100644
--- a/glib/tests/string.c
+++ b/glib/tests/string.c
@@ -225,6 +225,26 @@ test_string_append (void)
 
   g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreore");
 
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null (g_string_append (NULL, NULL));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null ((g_string_append) (NULL, NULL));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append (string, NULL) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append) (string, NULL) == string);
+  g_test_assert_expected_messages ();
+
   g_string_free (string, TRUE);
   g_free (tmp);
 
@@ -235,6 +255,39 @@ test_string_append (void)
   g_string_append_len (string, "more", -1);
   (g_string_append_len) (string, "ore", -1);
 
+  g_assert_true (g_string_append_len (string, NULL, 0) == string);
+  g_assert_true ((g_string_append_len) (string, NULL, 0) == string);
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null (g_string_append_len (NULL, NULL, -1));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*string != NULL*failed*");
+  g_assert_null ((g_string_append_len) (NULL, NULL, -1));
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append_len (string, NULL, -1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append_len) (string, NULL, -1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true (g_string_append_len (string, NULL, 1) == string);
+  g_test_assert_expected_messages ();
+
+  g_test_expect_message (G_LOG_DOMAIN, G_LOG_LEVEL_CRITICAL,
+                         "*assertion*val != NULL*failed*");
+  g_assert_true ((g_string_append_len) (string, NULL, 1) == string);
+  g_test_assert_expected_messages ();
+
   g_assert_cmpstr (string->str, ==, "firsthalflasthalfmoreore");
   g_string_free (string, TRUE);
 }