diff --git a/tests/util_test.c b/tests/util_test.c
index 8863e33..0df972b 100644
--- a/tests/util_test.c
+++ b/tests/util_test.c
@@ -279,8 +279,29 @@ static void test_filter_printf(void) {
     printf("test_filter_printf OK\n");
 }
 
+static void test_rfc4515_replace(void) {
+    assert(rfc4515_length("", NULL) == 1);
+    assert(rfc4515_length(" ", NULL) == 2);
+    assert(rfc4515_length("test1234567890_.", NULL) == 17);
+    assert(rfc4515_length("\\test\\test\\", NULL) == 18);
+    assert(rfc4515_length("*test*test*", NULL) == 18);
+    assert(rfc4515_length("(test(test(", NULL) == 18);
+    assert(rfc4515_length(")test)test)", NULL) == 18);
+    assert(rfc4515_length("\\\\**(())", NULL) == 25);
+
+    assert(!strcmp(rfc4515_replace(""), ""));
+    assert(!strcmp(rfc4515_replace(" "), " "));
+    assert(!strcmp(rfc4515_replace("test1234567890_."), "test1234567890_."));
+    assert(!strcmp(rfc4515_replace("\\test\\test\\"), "\\5Ctest\\5Ctest\\5C"));
+    assert(!strcmp(rfc4515_replace("*test*test*"), "\\2Atest\\2Atest\\2A"));
+    assert(!strcmp(rfc4515_replace("(test(test("), "\\28test\\28test\\28"));
+    assert(!strcmp(rfc4515_replace(")test)test)"), "\\29test\\29test\\29"));
+    assert(!strcmp(rfc4515_replace("\\\\**(())"), "\\5C\\5C\\2A\\2A\\28\\28\\29\\29"));
+    printf("test_rfc4515_replace OK\n");
+}
 int main (void) {
   test_filter_printf();
+  test_rfc4515_replace();
   test_get_user_cfgfile_path();
   test_check_user_token();
 #if HAVE_CR
diff --git a/util.c b/util.c
index d157678..588374f 100644
--- a/util.c
+++ b/util.c
@@ -783,7 +783,66 @@ size_t filter_result_len(const char *filter, const char *user, char *output) {
 }
 
 char *filter_printf(const char *filter, const char *user) {
-  char *result = malloc(filter_result_len(filter, user, NULL));
-  filter_result_len(filter, user, result);
+  char *user_rfc4515 = rfc4515_replace(user);
+  char *result = malloc(filter_result_len(filter, user_rfc4515, NULL));
+  filter_result_len(filter, user_rfc4515, result);
+  free(user_rfc4515);
   return result;
 }
+
+size_t rfc4515_length (const char* in, char* out)
+{
+    const char* pos = NULL;
+    size_t result = 0;
+    const char specials[] = "\\*()";
+
+    do
+    {
+        pos = strpbrk(in, specials);
+
+        size_t len = 0;
+        if(pos != NULL)
+        {
+            len = pos - in;
+        }
+        else
+        {
+            len = strlen(in);
+        }
+
+        if(out != NULL)
+        {
+            strncpy(out, in, len);
+            out += len;
+        }
+
+        result += len;
+        in += len;
+
+        if(pos != NULL)
+        {
+            if(out != NULL)
+            {
+              snprintf(out, 4, "%c%02X", 0x5c, *pos);
+              out += 3;
+            }
+
+            in += sizeof(char);
+            result += 3;
+        }
+    } while (pos != NULL);
+
+    if(out != NULL)
+    {
+        *out = '\0';
+    }
+
+    return (result + sizeof(char));
+}
+
+char* rfc4515_replace(const char* in)
+{
+    char* result = (char*)malloc(rfc4515_length(in, NULL));
+    rfc4515_length (in, result);
+    return result;
+}
diff --git a/util.h b/util.h
index 3a36978..1d1b2eb 100644
--- a/util.h
+++ b/util.h
@@ -103,4 +103,7 @@ int challenge_response(YK_KEY *yk, int slot,
 size_t filter_result_len(const char *filter, const char *user, char *output);
 char *filter_printf(const char *filter, const char *user);
 
+size_t rfc4515_length ( const char* in, char* out );
+char* rfc4515_replace ( const char* in );
+
 #endif /* __PAM_YUBICO_UTIL_H_INCLUDED__ */