diff --git a/src/_zkapauthorizer/tests/strategies.py b/src/_zkapauthorizer/tests/strategies.py
index d8b48e243af5b1161ce77d4376ea9af47bbace8d..d468030d111774a4090ad3e544952b4651895f56 100644
--- a/src/_zkapauthorizer/tests/strategies.py
+++ b/src/_zkapauthorizer/tests/strategies.py
@@ -142,7 +142,7 @@ def tahoe_config_texts(storage_client_plugins, shares):
     def merge_shares(shares, the_rest):
         for (k, v) in zip(("needed", "happy", "total"), shares):
             if v is not None:
-                the_rest["shares." + k] = "{}".format(v)
+                the_rest["shares." + k] = f"{v}"
         return the_rest
 
     client_section = builds(
@@ -249,7 +249,7 @@ def server_configurations(signing_key_path):
             {
                 "pass-value":
                 # The configuration is ini so everything is always a byte string!
-                integers(min_value=1).map(lambda v: "{}".format(v).encode("ascii")),
+                integers(min_value=1).map(lambda v: f"{v}".encode("ascii")),
             }
         ),
         just({}),
diff --git a/src/_zkapauthorizer/tests/test_client_resource.py b/src/_zkapauthorizer/tests/test_client_resource.py
index e72c0b927593035fc5092bf361ad3f8029b0347f..5cedaf488b906be6bdf2ba6301ee9e745001c8ae 100644
--- a/src/_zkapauthorizer/tests/test_client_resource.py
+++ b/src/_zkapauthorizer/tests/test_client_resource.py
@@ -331,7 +331,7 @@ class GetTokenCountTests(TestCase):
             token_config = {}
         else:
             expected_count = token_count
-            token_config = {"default-token-count": "{}".format(expected_count)}
+            token_config = {"default-token-count": f"{expected_count}"}
 
         config_text = config_string_from_sections(
             [
@@ -567,7 +567,7 @@ class UnblindedTokenTests(TestCase):
         )
         self.addDetail(
             "requesting result",
-            text_content("{}".format(vars(requesting.result))),
+            text_content(f"{vars(requesting.result)}"),
         )
         self.assertThat(
             requesting,
@@ -615,7 +615,7 @@ class UnblindedTokenTests(TestCase):
         )
         self.addDetail(
             "requesting result",
-            text_content("{}".format(vars(requesting.result))),
+            text_content(f"{vars(requesting.result)}"),
         )
         self.assertThat(
             requesting,
@@ -670,7 +670,7 @@ class UnblindedTokenTests(TestCase):
         )
         self.addDetail(
             "requesting result",
-            text_content("{}".format(vars(requesting.result))),
+            text_content(f"{vars(requesting.result)}"),
         )
         self.assertThat(
             requesting,
@@ -958,7 +958,7 @@ class VoucherTests(TestCase):
         )
         self.addDetail(
             "requesting result",
-            text_content("{}".format(vars(requesting.result))),
+            text_content(f"{vars(requesting.result)}"),
         )
         self.assertThat(
             requesting,
@@ -990,7 +990,7 @@ class VoucherTests(TestCase):
         )
         self.addDetail(
             "requesting result",
-            text_content("{}".format(vars(requesting.result))),
+            text_content(f"{vars(requesting.result)}"),
         )
         self.assertThat(
             requesting,