diff --git a/promslog/flag/flag.go b/promslog/flag/flag.go
index 0a164fcc..34edb6ff 100644
--- a/promslog/flag/flag.go
+++ b/promslog/flag/flag.go
@@ -15,6 +15,8 @@
 // across Prometheus components.
 // It should typically only ever be imported by main packages.
 
+//go:build go1.21
+
 package flag
 
 import (
diff --git a/promslog/slog.go b/promslog/slog.go
index 930d5ac3..c38e3178 100644
--- a/promslog/slog.go
+++ b/promslog/slog.go
@@ -14,6 +14,9 @@
 // Package promslog defines standardised ways to initialize the Go standard
 // library's log/slog logger.
 // It should typically only ever be imported by main packages.
+
+//go:build go1.21
+
 package promslog
 
 import (
diff --git a/promslog/slog_test.go b/promslog/slog_test.go
index bcdca361..a82388fd 100644
--- a/promslog/slog_test.go
+++ b/promslog/slog_test.go
@@ -11,6 +11,8 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+//go:build go1.21
+
 package promslog
 
 import (