diff --git a/src/core/tools/qchar.cpp b/src/core/tools/qchar.cpp
index ad2af9126..1cc147808 100644
--- a/src/core/tools/qchar.cpp
+++ b/src/core/tools/qchar.cpp
@@ -612,6 +612,16 @@ bool QChar::isSpace() const
 {
     if(ucs >= 9 && ucs <= 13)
         return true;
+    const int8_t category = u_charType(ucs);
+    switch (category) {
+        case U_SPACE_SEPARATOR:
+        case U_LINE_SEPARATOR:
+        case U_PARAGRAPH_SEPARATOR:
+            return true;
+        default:
+            return false;
+    }
+    // special characters check
     return u_isblank(ucs);
 }
 
@@ -676,7 +686,21 @@ bool QChar::isLetterOrNumber() const
     if (is_ascii_char(ucs)) {
         return is_ascii_letterornumber(ucs);
     }
-    return u_isalnum(ucs);
+    const int8_t category = u_charType(ucs);
+    switch (category) {
+        case U_UPPERCASE_LETTER:
+        case U_LOWERCASE_LETTER:
+        case U_TITLECASE_LETTER:
+        case U_MODIFIER_LETTER:
+        case U_OTHER_LETTER:
+        case U_DECIMAL_DIGIT_NUMBER:
+        case U_LETTER_NUMBER:
+        case U_OTHER_NUMBER:
+            return true;
+        default:
+            return false;
+    }
+    return false;
 }