diff --git a/filesystem/fat32/directoryentry.go b/filesystem/fat32/directoryentry.go
index 08cb2ec4..86f119f2 100644
--- a/filesystem/fat32/directoryentry.go
+++ b/filesystem/fat32/directoryentry.go
@@ -103,7 +103,7 @@ func (de *directoryEntry) toBytes() ([]byte, error) {
 	}
 
 	if de.lowercaseExtension {
-		dosBytes[12] |= 0x04
+		dosBytes[12] |= 0x10
 	}
 	if de.lowercaseShortname {
 		dosBytes[12] |= 0x08
@@ -161,7 +161,7 @@ byteLoop:
 		isArchiveDirty := b[i+11]&0x20 == 0x20
 		isVolumeLabel := b[i+11]&0x08 == 0x08
 		lowercaseShortname := b[i+12]&0x08 == 0x08
-		lowercaseExtension := b[i+12]&0x04 == 0x04
+		lowercaseExtension := b[i+12]&0x10 == 0x10
 
 		entry := directoryEntry{
 			filenameLong:       lfn,
diff --git a/filesystem/fat32/fat32.go b/filesystem/fat32/fat32.go
index b13c42aa..6e5a7463 100644
--- a/filesystem/fat32/fat32.go
+++ b/filesystem/fat32/fat32.go
@@ -511,7 +511,7 @@ func (fs *FileSystem) ReadDir(p string) ([]os.FileInfo, error) {
 		}
 		fileExtension := e.fileExtension
 		if e.lowercaseExtension {
-			shortName = strings.ToLower(fileExtension)
+			fileExtension = strings.ToLower(fileExtension)
 		}
 		if fileExtension != "" {
 			shortName = fmt.Sprintf("%s.%s", shortName, fileExtension)
@@ -553,7 +553,7 @@ func (fs *FileSystem) OpenFile(p string, flag int) (filesystem.File, error) {
 		if e.fileExtension != "" {
 			shortName += "." + e.fileExtension
 		}
-		if e.filenameLong != filename && shortName != filename {
+		if !strings.EqualFold(e.filenameLong, filename) && !strings.EqualFold(shortName, filename) {
 			continue
 		}
 		// cannot do anything with directories
@@ -840,7 +840,7 @@ func (fs *FileSystem) readDirWithMkdir(p string, doMake bool) (*Directory, []*di
 			// match is determined by any one of:
 			// - long filename == provided name
 			// - uppercase(short filename) == uppercase(provided name)
-			if e.filenameLong != subp && !strings.EqualFold(e.filenameShort, subp) {
+			if !strings.EqualFold(e.filenameLong, subp) && !strings.EqualFold(e.filenameShort, subp) {
 				continue
 			}
 			if !e.isSubdirectory {
diff --git a/filesystem/fat32/fat32_test.go b/filesystem/fat32/fat32_test.go
index 62c6e3ad..1bc189e0 100644
--- a/filesystem/fat32/fat32_test.go
+++ b/filesystem/fat32/fat32_test.go
@@ -977,3 +977,84 @@ func TestFat32MkdirCases(t *testing.T) {
 		t.Fatalf("expected 1 file, found %d", len(files))
 	}
 }
+
+func Test83Lowercase(t *testing.T) {
+	// get a temporary working file
+	f, err := tmpFat32(true, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if keepTmpFiles == "" {
+		defer os.Remove(f.Name())
+	} else {
+		fmt.Println(f.Name())
+	}
+	fileInfo, err := f.Stat()
+	if err != nil {
+		t.Fatalf("error getting file info for tmpfile %s: %v", f.Name(), err)
+	}
+	fs, err := fat32.Read(f, fileInfo.Size(), 0, 512)
+	if err != nil {
+		t.Fatalf("error reading fat32 filesystem from %s: %v", f.Name(), err)
+	}
+
+	// Ensure using correct masks for lowercase shortname and extension (bits 3 and 4, zero-based)
+	files, err := fs.ReadDir("/lower83")
+	if err != nil {
+		t.Fatal(err)
+	}
+	expected := []string{"lower.low", "lower.UPP", "UPPER.low"}
+	i := 0
+	for _, file := range files {
+		if file.Name() == "." || file.Name() == ".." {
+			continue
+		}
+		if file.Name() != expected[i] {
+			t.Errorf("got %q, expected %q", file.Name(), expected[i])
+		}
+		i++
+	}
+}
+
+func TestOpenFileCaseInsensitive(t *testing.T) {
+	// get a temporary working file
+	f, err := tmpFat32(true, 0, 0)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if keepTmpFiles == "" {
+		defer os.Remove(f.Name())
+	} else {
+		fmt.Println(f.Name())
+	}
+	fileInfo, err := f.Stat()
+	if err != nil {
+		t.Fatalf("error getting file info for tmpfile %s: %v", f.Name(), err)
+	}
+	fs, err := fat32.Read(f, fileInfo.Size(), 0, 512)
+	if err != nil {
+		t.Fatalf("error reading fat32 filesystem from %s: %v", f.Name(), err)
+	}
+
+	// Ensure openfile is case-insensitive for the 8.3 name as well as the long name
+	paths := []string{
+		// The actual name
+		"/lower83/lower.low",
+		// Same name but different extension case
+		"/lower83/lower.LOW",
+		// Same name but different base case
+		"/lower83/LOWER.LOW",
+		// Actual name/case of non-8.3 file
+		"/tercer_archivo",
+		// Same name but uppercase
+		"/TERCER_ARCHIVO",
+	}
+	for _, path := range paths {
+		file, err := fs.OpenFile(path, os.O_RDONLY)
+		if err != nil {
+			t.Errorf("error opening %s: %v\n", path, err)
+		} else {
+			file.Close()
+		}
+	}
+}
diff --git a/filesystem/fat32/testdata/mkfat32.sh b/filesystem/fat32/testdata/mkfat32.sh
index b235e2bf..5beeee57 100755
--- a/filesystem/fat32/testdata/mkfat32.sh
+++ b/filesystem/fat32/testdata/mkfat32.sh
@@ -28,6 +28,10 @@ mcopy -i /data/fat32.img /CORTO1.TXT ::/
 mcopy -i /data/fat32.img '/Un archivo con nombre largo.dat' ::/
 mcopy -i /data/fat32.img '/tercer_archivo' ::/
 mcopy -i /data/fat32.img '/some_long_embedded_nameא' ::/foo/bar
+mmd -i /data/fat32.img ::/lower83
+mcopy -i /data/fat32.img /CORTO1.TXT ::/lower83/lower.low
+mcopy -i /data/fat32.img /CORTO1.TXT ::/lower83/lower.UPP
+mcopy -i /data/fat32.img /CORTO1.TXT ::/lower83/UPPER.low
 
 i=0
 until [ $i -gt 75 ]; do mmd -i /data/fat32.img ::/foo/dir${i}; i=$(( $i+1 )); done