diff --git a/fmriprep/_warnings.py b/fmriprep/_warnings.py
index 60b3c2c9..bf738091 100644
--- a/fmriprep/_warnings.py
+++ b/fmriprep/_warnings.py
@@ -35,7 +35,7 @@ def _warn(message, category=None, stacklevel=1, source=None):
         category = type(category).__name__
         category = category.replace('type', 'WARNING')
 
-    logging.getLogger('py.warnings').warning(f"{category or 'WARNING'}: {message}")
+    logging.getLogger('py.warnings').warning("%s: %s", category or 'WARNING', message)
 
 
 def _showwarning(message, category, filename, lineno, file=None, line=None):
diff --git a/fmriprep/interfaces/reports.py b/fmriprep/interfaces/reports.py
index 8f26c374..8f2a6270 100644
--- a/fmriprep/interfaces/reports.py
+++ b/fmriprep/interfaces/reports.py
@@ -365,7 +365,8 @@ def get_world_pedir(ornt, pe_direction):
                 if flip[not inv].startswith(axcode):
                     return '-'.join(flip)
     LOGGER.warning(
-        'Cannot determine world direction of phase encoding. '
-        f'Orientation: {ornt}; PE dir: {pe_direction}'
+        'Cannot determine world direction of phase encoding. Orientation: %s; PE dir: %s',
+        ornt,
+        pe_direction,
     )
     return 'Could not be determined - assuming Anterior-Posterior'
diff --git a/fmriprep/workflows/bold/stc.py b/fmriprep/workflows/bold/stc.py
index 20047418..f414f830 100644
--- a/fmriprep/workflows/bold/stc.py
+++ b/fmriprep/workflows/bold/stc.py
@@ -115,7 +115,7 @@ def init_bold_stc_wf(
     inputnode = pe.Node(niu.IdentityInterface(fields=['bold_file', 'skip_vols']), name='inputnode')
     outputnode = pe.Node(niu.IdentityInterface(fields=['stc_file']), name='outputnode')
 
-    LOGGER.log(25, f'BOLD series will be slice-timing corrected to an offset of {tzero:.3g}s.')
+    LOGGER.log(25, 'BOLD series will be slice-timing corrected to an offset of %.3gs.', tzero)
 
     # It would be good to fingerprint memory use of afni.TShift
     slice_timing_correction = pe.Node(
diff --git a/pyproject.toml b/pyproject.toml
index 6af2e831..f32416f8 100644
--- a/pyproject.toml
+++ b/pyproject.toml
@@ -170,6 +170,7 @@ extend-select = [
   # "EM",
   "EXE",
   "FA",
+  "G",
   "ISC",
   "ICN",
   "PT",