diff --git a/json_object.c b/json_object.c
index 04164d0..c2463c1 100644
--- a/json_object.c
+++ b/json_object.c
@@ -969,7 +969,8 @@ static int json_object_double_to_json_string_format(struct json_object *jso, str
 					p = q;
 			}
 			/* drop trailing zeroes */
-			*(++p) = 0;
+			if (*p != 0)
+				*(++p) = 0;
 			size = p - buf;
 		}
 	}
diff --git a/tests/test_set_serializer.c b/tests/test_set_serializer.c
index db1c187..b5c1979 100644
--- a/tests/test_set_serializer.c
+++ b/tests/test_set_serializer.c
@@ -26,7 +26,7 @@ static int custom_serializer(struct json_object *o, struct printbuf *pb, int lev
 
 int main(int argc, char **argv)
 {
-	json_object *my_object;
+	json_object *my_object, *my_sub_object;
 
 	MC_SET_DEBUG(1);
 
@@ -67,5 +67,17 @@ int main(int argc, char **argv)
 	json_object_put(my_object);
 	assert(freeit_was_called);
 
+	// ============================================
+
+	my_object = json_object_new_object();
+	my_sub_object = json_object_new_double(1.0);
+	json_object_object_add(my_object, "double", my_sub_object);
+	printf("Check that the custom serializer does not include nul byte:\n");
+	json_object_set_serializer(my_sub_object, json_object_double_to_json_string, "%125.0f,", NULL);
+	printf("my_object.to_string(custom serializer)=%s\n",
+	       json_object_to_json_string_ext(my_object, JSON_C_TO_STRING_NOZERO));
+
+	json_object_put(my_object);
+
 	return 0;
 }
diff --git a/tests/test_set_serializer.expected b/tests/test_set_serializer.expected
index ad44a90..9629dd6 100644
--- a/tests/test_set_serializer.expected
+++ b/tests/test_set_serializer.expected
@@ -8,3 +8,5 @@ Check that the custom serializer isn't free'd until the last json_object_put:
 my_object.to_string(custom serializer)=Custom Output
 Next line of output should be from the custom freeit function:
 freeit, value=123
+Check that the custom serializer does not include nul byte:
+my_object.to_string(custom serializer)={"double":                                                                                                                            1.}