diff --git a/qurator/dinglehopper/substitute_equivalences.py b/qurator/dinglehopper/substitute_equivalences.py
index 1b7e0cf..39be276 100644
--- a/qurator/dinglehopper/substitute_equivalences.py
+++ b/qurator/dinglehopper/substitute_equivalences.py
@@ -1,21 +1,15 @@
 import unicodedata
 
 
-def substitute_equivalences(s):
+def unjoin_ligatures(s):
+    """Unjoin ligatures, i.e. ff becomes ff."""
 
-    # These are for OCR-D GT vs Tesseract frk vs Calamari GT4HistOCR
-    # It might make sense to use different rules for GT and for the different OCR
     equivalences = {
-        '': 'ü',
         '': 'ſſ',
         "\ueba7": 'ſſi',  # MUFI: LATIN SMALL LIGATURE LONG S LONG S I
-        '': 'ä',
         '': 'ch',
-        '==': '–',  # → en-dash
-        '—': '–',   # em-dash → en-dash
         '': 'ck',
         '': 'll',
-        '': 'ö',
         '': 'ſi',
         '': 'ſt',
         'fi': 'fi',
@@ -23,12 +17,7 @@ def substitute_equivalences(s):
         'fl': 'fl',
         'ffi': 'ffi',
         '': 'ct',
-        '’': '\'',
-        '⸗': '-',
         '': 'tz',       # MUFI: LATIN SMALL LIGATURE TZ
-        'aͤ': 'ä',        # LATIN SMALL LETTER A, COMBINING LATIN SMALL LETTER E
-        'oͤ': 'ö',        # LATIN SMALL LETTER O, COMBINING LATIN SMALL LETTER E
-        'uͤ': 'ü',        # LATIN SMALL LETTER U, COMBINING LATIN SMALL LETTER E
         '\uf532': 'as',  # eMOP: Latin small ligature as
         '\uf533': 'is',  # eMOP: Latin small ligature is
         '\uf534': 'us',  # eMOP: Latin small ligature us
@@ -37,10 +26,32 @@ def substitute_equivalences(s):
         '\uE8BF': 'q&',  # MUFI: LATIN SMALL LETTER Q LIGATED WITH FINAL ET  XXX How to replace this correctly?
         '\uEBA5': 'ſp',  # MUFI: LATIN SMALL LIGATURE LONG S P
         'st': 'st',      # U+FB06 LATIN SMALL LIGATURE ST
+    }
+    s = unicodedata.normalize('NFC', s)
+    for fr, to in equivalences.items():
+        s = s.replace(fr, to)
+    return s
+
+
+def substitute_equivalences(s):
+    # These are for OCR-D GT vs Tesseract frk vs Calamari GT4HistOCR
+    # It might make sense to use different rules for GT and for the different OCR
+    equivalences = {
+        '': 'ü',
+        '': 'ä',
+        '==': '–',  # → en-dash
+        '—': '–',   # em-dash → en-dash
+        '': 'ö',
+        '’': '\'',
+        '⸗': '-',
+        'aͤ': 'ä',        # LATIN SMALL LETTER A, COMBINING LATIN SMALL LETTER E
+        'oͤ': 'ö',        # LATIN SMALL LETTER O, COMBINING LATIN SMALL LETTER E
+        'uͤ': 'ü',        # LATIN SMALL LETTER U, COMBINING LATIN SMALL LETTER E
         '\uF50E': 'q́'    # U+F50E LATIN SMALL LETTER Q WITH ACUTE ACCENT
     }
 
     s = unicodedata.normalize('NFC', s)
+    s = unjoin_ligatures(s)
     for fr, to in equivalences.items():
         s = s.replace(fr, to)
     return s