diff --git a/src/ly_common.c b/src/ly_common.c
index a9bfbccc9..c1ad0a588 100644
--- a/src/ly_common.c
+++ b/src/ly_common.c
@@ -724,7 +724,6 @@ ly_pat_compile_posix(const char *pattern, void **pat_comp, struct ly_err_item **
 static LY_ERR
 ly_pat_compile_xmlschema_chblocks_xmlschema2perl(const char *pattern, char **regex, struct ly_err_item **err)
 {
-#define URANGE_LEN 19
     char *ublock2urange[][2] = {
         {"BasicLatin", "[\\x{0000}-\\x{007F}]"},
         {"Latin-1Supplement", "[\\x{0080}-\\x{00FF}]"},
@@ -829,15 +828,6 @@ ly_pat_compile_xmlschema_chblocks_xmlschema2perl(const char *pattern, char **reg
         }
         end = (ptr - perl_regex) + 1;
 
-        /* need more space */
-        if (end - start < URANGE_LEN) {
-            perl_regex = ly_realloc(perl_regex, strlen(perl_regex) + (URANGE_LEN - (end - start)) + 1);
-            *regex = perl_regex;
-            if (!perl_regex) {
-                return ly_err_new(err, LY_EMEM, 0, NULL, NULL, LY_EMEM_MSG);
-            }
-        }
-
         /* find our range */
         for (idx = 0; ublock2urange[idx][0]; ++idx) {
             if (!strncmp(perl_regex + start + ly_strlen_const("\\p{Is"),
@@ -851,6 +841,17 @@ ly_pat_compile_xmlschema_chblocks_xmlschema2perl(const char *pattern, char **reg
         }
         ublock = idx;
 
+        /* need more space */
+        size_t urange_len = strlen(ublock2urange[ublock][1]);
+
+        if (end - start < urange_len) {
+            perl_regex = ly_realloc(perl_regex, strlen(perl_regex) + (urange_len - (end - start)) + 1);
+            *regex = perl_regex;
+            if (!perl_regex) {
+                return ly_err_new(err, LY_EMEM, 0, NULL, NULL, LY_EMEM_MSG);
+            }
+        }
+
         /* make the space in the string and replace the block (but we cannot include brackets if it was already enclosed in them) */
         for (idx2 = 0, idx = 0; idx2 < start; ++idx2) {
             if ((perl_regex[idx2] == '[') && (!idx2 || (perl_regex[idx2 - 1] != '\\'))) {
@@ -863,11 +864,11 @@ ly_pat_compile_xmlschema_chblocks_xmlschema2perl(const char *pattern, char **reg
         }
         if (idx) {
             /* skip brackets */
-            memmove(perl_regex + start + (URANGE_LEN - 2), perl_regex + end, strlen(perl_regex + end) + 1);
-            memcpy(perl_regex + start, ublock2urange[ublock][1] + 1, URANGE_LEN - 2);
+            memmove(perl_regex + start + (urange_len - 2), perl_regex + end, strlen(perl_regex + end) + 1);
+            memcpy(perl_regex + start, ublock2urange[ublock][1] + 1, urange_len - 2);
         } else {
-            memmove(perl_regex + start + URANGE_LEN, perl_regex + end, strlen(perl_regex + end) + 1);
-            memcpy(perl_regex + start, ublock2urange[ublock][1], URANGE_LEN);
+            memmove(perl_regex + start + urange_len, perl_regex + end, strlen(perl_regex + end) + 1);
+            memcpy(perl_regex + start, ublock2urange[ublock][1], urange_len);
         }
     }
 
diff --git a/tests/utests/types/string.c b/tests/utests/types/string.c
index e0ef60411..23210a70c 100644
--- a/tests/utests/types/string.c
+++ b/tests/utests/types/string.c
@@ -863,6 +863,22 @@ test_data_xml(void **state)
     UTEST_INVALID_MODULE(schema, LYS_IN_YANG, NULL, LY_EVALID);
     CHECK_LOG_CTX("Regular expression \"[\\p{IsBasicLatin}\\p{IsUnknownUnicodeBlock}]+\" "
             "is not valid (\"UnknownUnicodeBlock}]+\": unknown block name).", "/T_UB_8:port", 0);
+
+    schema = MODULE_CREATE_YANG("T_UB_9", "leaf port {type string { pattern "
+            "'[\\p{IsSpecials}]+';}}");
+    UTEST_ADD_MODULE(schema, LYS_IN_YANG, NULL, NULL);
+    TEST_SUCCESS_XML("T_UB_9", "&#xFFFA;&#xFFFD;", STRING, "\xef\xbf\xba\xef\xbf\xbd");
+
+    schema = MODULE_CREATE_YANG("T_UB_10", "leaf port {type string { pattern "
+            "'[\\p{IsSpecials}]+';}}");
+    UTEST_ADD_MODULE(schema, LYS_IN_YANG, NULL, NULL);
+    TEST_ERROR_XML("T_UB_10", "&#xFFDF;&#xFFFD;");
+    CHECK_LOG_CTX("Unsatisfied pattern - \"\xef\xbf\x9f\xef\xbf\xbd\" does not match \"[\\p{IsSpecials}]+\".", "/T_UB_10:port", 1);
+
+    schema = MODULE_CREATE_YANG("T_UB_11", "leaf port {type string { pattern "
+            "'[\\p{IsSpecials}]+';}}");
+    UTEST_ADD_MODULE(schema, LYS_IN_YANG, NULL, NULL);
+    TEST_SUCCESS_XML("T_UB_11", "&#xFEFF;&#xFFFD;", STRING, "\xef\xbb\xbf\xef\xbf\xbd");
 }
 
 static void