diff --git a/src/pymatgen/io/xtb/inputs.py b/src/pymatgen/io/xtb/inputs.py
index b9dc3352717..cbc6a413dbe 100644
--- a/src/pymatgen/io/xtb/inputs.py
+++ b/src/pymatgen/io/xtb/inputs.py
@@ -83,7 +83,7 @@ def constrains_template(molecule, reference_fnm, constraints) -> str:
         for idx, val in enumerate(atoms_for_mtd):
             if val + 1 not in atoms_for_mtd:
                 interval_list.append(val)
-                if idx != len(atoms_for_mtd):
+                if idx != len(atoms_for_mtd) - 1:
                     interval_list.append(atoms_for_mtd[idx + 1])
         allowed_mtd_string = ",".join(
             [f"{interval_list[i]}-{interval_list[i + 1]}" for i in range(len(interval_list)) if i % 2 == 0]
diff --git a/src/pymatgen/io/xtb/outputs.py b/src/pymatgen/io/xtb/outputs.py
index 3b9deb11a9d..60ca8c52834 100644
--- a/src/pymatgen/io/xtb/outputs.py
+++ b/src/pymatgen/io/xtb/outputs.py
@@ -70,12 +70,12 @@ def _parse_crest_output(self):
             print(f"Input file {split_cmd[0]} not found")
 
         # Get CREST input flags
-        for i, entry in enumerate(split_cmd, start=1):
+        for i, entry in enumerate(split_cmd):
             value = None
             if entry and "-" in entry:
                 option = entry[1:]
-                if i < len(split_cmd) and "-" not in entry:
-                    value = entry
+                if i < len(split_cmd) and "-" not in split_cmd[i + 1]:
+                    value = split_cmd[i + 1]
                 self.cmd_options[option] = value
         # Get input charge for decorating parsed molecules
         chg = 0