diff --git a/safe/converter.py b/safe/converter.py
index 7611168..7bd0ee0 100644
--- a/safe/converter.py
+++ b/safe/converter.py
@@ -332,7 +332,13 @@ def encoder(
             val = str(starting_num) if starting_num < 10 else f"%{starting_num}"
             # we cannot have anything of the form "\([@=-#-$/\]*\d+\)"
             attach_regexp = re.compile(r"(" + re.escape(attach) + r")")
-            scaffold_str = attach_regexp.sub(val, scaffold_str)
+            # check if we have at least 2 matches, if not, we have a dummy
+            n_matches = len(attach_regexp.findall(scaffold_str))
+            scaffold_str = (
+                attach_regexp.sub(val, scaffold_str)
+                if n_matches > 1
+                else scaffold_str.replace(attach, "*")
+            )
             starting_num += 1
         # now we need to remove all the parenthesis around digit only number
         wrong_attach = re.compile(r"\(([\%\d]*)\)")
diff --git a/tests/test_safe.py b/tests/test_safe.py
index fdfc288..b266249 100644
--- a/tests/test_safe.py
+++ b/tests/test_safe.py
@@ -85,6 +85,7 @@ def test_rdkit_smiles_parser_issues():
         "c1cc2c(cc1[C@@H]1CCC[NH2+]1)OCCO2",
         "[13C]1CCCCC1C[238U]C[NH3+]",
         "COC[CH2:1][CH2:2]O[CH:2]C[OH:3]",
+        "C1*CCC1COO",
     ],
 )
 def test_bracket_smiles_issues(input_sm):