diff --git a/extractor/text.go b/extractor/text.go
index f16645f5..5872c480 100644
--- a/extractor/text.go
+++ b/extractor/text.go
@@ -245,7 +245,7 @@ func (e *Extractor) extractPageText(contents string, resources *model.PdfPageRes
 					return err
 				}
 				err = to.setFont(name, size)
-				to.invalidFont = unsupportedFontErr(err)
+				to.invalidFont = errors.Is(err, core.ErrNotSupported)
 				if err != nil && !to.invalidFont {
 					return err
 				}
@@ -372,23 +372,6 @@ func (e *Extractor) extractPageText(contents string, resources *model.PdfPageRes
 	return pageText, state.numChars, state.numMisses, err
 }
 
-// unsupportedFontErr returns true if `err` indicated that the selected font or encoding is not supported.
-func unsupportedFontErr(err error) bool {
-	if err == model.ErrFontNotSupported ||
-		err == model.ErrType1CFontNotSupported ||
-		err == model.ErrType3FontNotSupported ||
-		err == model.ErrTTCmapNotSupported {
-		return true
-	}
-	if err == nil {
-		return false
-	}
-	errStr := err.Error()
-	return strings.Contains(errStr, "unsupported font encoding:") ||
-		strings.Contains(errStr, "unexpected subtable format:") ||
-		strings.Contains(errStr, "fonts based on PostScript outlines are not supported")
-}
-
 // textResult is used for holding results of PDF form processig
 type textResult struct {
 	pageText  PageText
diff --git a/internal/textencoding/simple.go b/internal/textencoding/simple.go
index bd209beb..ebd5592c 100644
--- a/internal/textencoding/simple.go
+++ b/internal/textencoding/simple.go
@@ -55,7 +55,7 @@ func NewSimpleTextEncoder(baseName string, differences map[CharCode]GlyphName) (
 	fnc, ok := simple[baseName]
 	if !ok {
 		common.Log.Debug("ERROR: NewSimpleTextEncoder. Unknown encoding %q", baseName)
-		return nil, fmt.Errorf("unsupported font encoding: %q", baseName)
+		return nil, fmt.Errorf("unsupported font encoding: %q (%w)", baseName, core.ErrNotSupported)
 	}
 	enc := fnc()
 	if len(differences) != 0 {
diff --git a/model/const.go b/model/const.go
index d6efcac4..ff2f1f4e 100644
--- a/model/const.go
+++ b/model/const.go
@@ -7,6 +7,9 @@ package model
 
 import (
 	"errors"
+	"fmt"
+
+	"github.com/unidoc/unipdf/v3/core"
 )
 
 // Errors when parsing/loading data in PDF.
@@ -18,8 +21,8 @@ var (
 	errRangeError               = errors.New("range check error")
 	ErrEncrypted                = errors.New("file needs to be decrypted first")
 	ErrNoFont                   = errors.New("font not defined")
-	ErrFontNotSupported         = errors.New("unsupported font")
-	ErrType1CFontNotSupported   = errors.New("Type1C fonts are not currently supported")
-	ErrType3FontNotSupported    = errors.New("Type3 fonts are not currently supported")
-	ErrTTCmapNotSupported       = errors.New("unsupported TrueType cmap format")
+	ErrFontNotSupported         = fmt.Errorf("unsupported font (%w)", core.ErrNotSupported)
+	ErrType1CFontNotSupported   = fmt.Errorf("Type1C fonts are not currently supported (%w)", core.ErrNotSupported)
+	ErrType3FontNotSupported    = fmt.Errorf("Type3 fonts are not currently supported (%w)", core.ErrNotSupported)
+	ErrTTCmapNotSupported       = fmt.Errorf("unsupported TrueType cmap format (%w)", core.ErrNotSupported)
 )
diff --git a/model/internal/fonts/ttfparser.go b/model/internal/fonts/ttfparser.go
index 42d0a94c..1e8d07cc 100644
--- a/model/internal/fonts/ttfparser.go
+++ b/model/internal/fonts/ttfparser.go
@@ -209,7 +209,8 @@ func (t *ttfParser) Parse() (TtfType, error) {
 	}
 	if version == "OTTO" {
 		// See https://docs.microsoft.com/en-us/typography/opentype/spec/otff
-		return TtfType{}, errors.New("fonts based on PostScript outlines are not supported")
+		return TtfType{}, fmt.Errorf("fonts based on PostScript outlines are not supported (%w)",
+			core.ErrNotSupported)
 	}
 	if version != "\x00\x01\x00\x00" && version != "true" {
 		// This is not an error. In the font_test.go example axes.txt we see version "true".
@@ -376,7 +377,7 @@ func (t *ttfParser) parseCmapSubtable31(offset31 int64) error {
 	t.f.Seek(int64(t.tables["cmap"])+offset31, os.SEEK_SET)
 	format := t.ReadUShort()
 	if format != 4 {
-		return fmt.Errorf("unexpected subtable format: %d", format)
+		return fmt.Errorf("unexpected subtable format: %d (%w)", format, core.ErrNotSupported)
 	}
 	t.Skip(2 * 2) // length, language
 	segCount := int(t.ReadUShort() / 2)