diff --git a/eval.py b/eval.py
index 594f799dbf850064690fd4a46ffd32ec7f6fa53a..61efc4250d444a966e70ec39ad324984958daea8 100755
--- a/eval.py
+++ b/eval.py
@@ -146,30 +146,30 @@ EMPER_FLAVORS = {
     },
     'no-sleep-computation-100us': {
         'meson_options': '-Dworker_sleep=false',
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     'no-sleep-no-completer-computation-100us': {
         'meson_options':
         '-Dworker_sleep=false -Dio_completer_behavior=maybe_wakeup',
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     'computation-100us': {
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     'completer-wakeup-computation-100us': {
         'meson_options': '-Dio_completer_behavior=maybe_wakeup',
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     'computation-10us': {
-        'server_cmd_suffix': ' 10'
+        'server_cmd_suffix': '10'
     },
     'completer-wakeup-computation-10us': {
         'meson_options': '-Dio_completer_behavior=maybe_wakeup',
-        'server_cmd_suffix': ' 10'
+        'server_cmd_suffix': '10'
     },
     'mutex-computation-100us': {
         'meson_options': '-Dio_cq_lock_implementation=mutex',
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     'first': {
         'checkout': EMPER_FIRST_CHECKOUT
@@ -182,21 +182,21 @@ EMPER_FLAVORS = {
     },
     '20-computation-100us': {
         'server_cmd_prefix': EMPER_20_WORKER_ENV_CMD,
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     '20-nopin-computation-100us': {
         'server_cmd_prefix':
         EMPER_20_WORKER_ENV_CMD + ' EMPER_PIN_WORKERS=false',
-        'server_cmd_suffix': ' 100'
+        'server_cmd_suffix': '100'
     },
     '20-computation-200us': {
         'server_cmd_prefix': EMPER_20_WORKER_ENV_CMD,
-        'server_cmd_suffix': ' 200'
+        'server_cmd_suffix': '200'
     },
     '20-nopin-computation-200us-nopin': {
         'server_cmd_prefix':
         EMPER_20_WORKER_ENV_CMD + ' EMPER_PIN_WORKERS=false',
-        'server_cmd_suffix': ' 200'
+        'server_cmd_suffix': '200'
     },
     'linked-futures-notify-all': {
         'checkout': EMPER_LINKED_FUTURE_CHECKOUT,
@@ -362,9 +362,10 @@ def prepare_emper_flavors(flavors, verbose=False):
     del SERVER_CMDS['emper']
 
     for flavor, desc in flavors.items():
-        server_cmd = desc.get(
-            'server_cmd_prefix', '') + emper_server_cmd.format(
-                flavor=flavor) + desc.get('server_cmd_suffix', '')
+        cmd_prefix = f'{desc["server_cmd_prefix"]} ' if 'server_cmd_prefix' in desc else ''
+        cmd_suffix = f' {desc["server_cmd_suffix"]}' if 'server_cmd_suffix' in desc else ''
+        cmd = emper_server_cmd.format(flavor=flavor)
+        server_cmd = f'{cmd_prefix}{cmd}{cmd_suffix}'
         SERVER_CMDS[f'emper-{flavor}'] = server_cmd
 
         # write flavor description into the flavor's result dir