Index: res/res_config_pgsql.c
===================================================================
--- res/res_config_pgsql.c	(revision 408084)
+++ res/res_config_pgsql.c	(working copy)
@@ -743,19 +743,23 @@
 	ast_str_set(&sql, 0, "UPDATE %s SET %s = '%s'", tablename, field->name, ast_str_buffer(escapebuf));
 
 	while ((field = field->next)) {
-		if (!find_column(table, field->name)) {
+		struct columns *column;
+		if (!(column = find_column(table, field->name))) {
 			ast_log(LOG_NOTICE, "Attempted to update column '%s' in table '%s', but column does not exist!\n", field->name, tablename);
 			continue;
 		}
 
-		ESCAPE_STRING(escapebuf, field->value);
-		if (pgresult) {
-			ast_log(LOG_ERROR, "PostgreSQL RealTime: detected invalid input: '%s'\n", field->value);
-			release_table(table);
-			return -1;
+		if (ast_strlen_zero(field->value) && !column->notnull) {
+			ast_str_append(&sql, 0, ", %s = NULL", field->name);
+		} else {
+			ESCAPE_STRING(escapebuf, field->value);
+			if (pgresult) {
+				ast_log(LOG_ERROR, "PostgreSQL RealTime: detected invalid input: '%s'\n", field->value);
+				release_table(table);
+				return -1;
+			}
+			ast_str_append(&sql, 0, ", %s = '%s'", field->name, ast_str_buffer(escapebuf));
 		}
-
-		ast_str_append(&sql, 0, ", %s = '%s'", field->name, ast_str_buffer(escapebuf));
 	}
 	release_table(table);