diff --git a/pymc/step_methods/hmc/base_hmc.py b/pymc/step_methods/hmc/base_hmc.py
index 7bc0e98a0b..1f45856ab9 100644
--- a/pymc/step_methods/hmc/base_hmc.py
+++ b/pymc/step_methods/hmc/base_hmc.py
@@ -60,7 +60,7 @@ def __init__(
         t0=10,
         adapt_step_size=True,
         step_rand=None,
-        **aesara_kwargs
+        **aesara_kwargs,
     ):
         """Set up Hamiltonian samplers with common structures.
 
@@ -165,7 +165,7 @@ def astep(self, q0):
             self.potential.raise_ok(q0.point_map_info)
             message_energy = (
                 "Bad initial energy, check any log probabilities that "
-                "are inf or -inf, nan or very small:\n{}".format(error_logp.to_string())
+                f"are inf or -inf, nan or very small:\n{error_logp}"
             )
             warning = SamplerWarning(
                 WarningType.BAD_ENERGY,