diff --git a/kazu/ontology_preprocessing/synonym_generation.py b/kazu/ontology_preprocessing/synonym_generation.py
index 1f56dd1f..b6f52d31 100644
--- a/kazu/ontology_preprocessing/synonym_generation.py
+++ b/kazu/ontology_preprocessing/synonym_generation.py
@@ -63,7 +63,7 @@ def __call__(
         )
         final_results: defaultdict[OntologyStringResource, set[Synonym]] = defaultdict(set)
         original_strings = {
-            syn.text for resource in ontology_resources for syn in resource.active_ner_synonyms()
+            syn.text for resource in ontology_resources for syn in resource.original_synonyms
         }
         for i, permutation_list in enumerate(synonym_gen_permutations):
             logger.info(
@@ -80,9 +80,7 @@ def __call__(
                     desc=f"generating synonyms for {generator.__class__.__name__}",
                 ):
 
-                    for syn in list(
-                        generated_results.get(resource, resource.active_ner_synonyms())
-                    ):
+                    for syn in list(generated_results.get(resource, resource.original_synonyms)):
                         new_strings = generator(syn.text)
                         for new_syn_text in new_strings:
                             if new_syn_text in original_strings:
diff --git a/kazu/tests/test_synonym_generators.py b/kazu/tests/test_synonym_generators.py
index 148f9278..37a653f7 100644
--- a/kazu/tests/test_synonym_generators.py
+++ b/kazu/tests/test_synonym_generators.py
@@ -249,6 +249,57 @@ def test_greek_substitution_dict_uncode_variants():
                 StringReplacement(replacement_dict={"-": [" ", "_"]}, include_greek=False),
             ],
         ),
+        (
+            OntologyStringResource(
+                original_synonyms=frozenset(
+                    [
+                        Synonym(
+                            text="estimate",
+                            mention_confidence=MentionConfidence.PROBABLE,
+                            case_sensitive=False,
+                        ),
+                        Synonym(
+                            text="estimate of",
+                            mention_confidence=MentionConfidence.PROBABLE,
+                            case_sensitive=False,
+                        ),
+                    ]
+                ),
+                behaviour=OntologyStringBehaviour.ADD_FOR_NER_AND_LINKING,
+            ),
+            set(),
+            [
+                StopWordRemover(),  # normally stopword remover would remove 'of' but since "estimate" is an original synonym
+                # CombinatorialSynonymGenerator will skip the alternative synonym generation
+            ],
+        ),
+        (
+            OntologyStringResource(
+                original_synonyms=frozenset(
+                    [
+                        Synonym(
+                            text="estimate of",
+                            mention_confidence=MentionConfidence.PROBABLE,
+                            case_sensitive=False,
+                        ),
+                    ]
+                ),
+                behaviour=OntologyStringBehaviour.ADD_FOR_NER_AND_LINKING,
+                alternative_synonyms=frozenset(
+                    [
+                        Synonym(
+                            text="estimate",
+                            mention_confidence=MentionConfidence.PROBABLE,
+                            case_sensitive=False,
+                        )
+                    ]
+                ),
+            ),
+            {"estimate"},
+            [
+                StopWordRemover(),
+            ],
+        ),
     ),
 )
 def test_CombinatorialSynonymGenerator(resource, expected_syns, generators):