diff --git a/cmd/shigola/cmd/cache/seed_purge.go b/cmd/shigola/cmd/cache/seed_purge.go
index 13908b26..5b1f66a7 100644
--- a/cmd/shigola/cmd/cache/seed_purge.go
+++ b/cmd/shigola/cmd/cache/seed_purge.go
@@ -438,8 +438,8 @@ func seedPurgeCommand(_ *cobra.Command, _ []string) (err error) {
 		}
 	}()
 
-	log.Info("zoom list: ", zooms)
-	log.Info("tile matrix set: ", seedPurgeGrid.ID())
+	log.Info("zoom list:", zooms)
+	log.Info("tile matrix set:", seedPurgeGrid.ID())
 	tileChannel := generateTilesForBounds(ctx, seedPurgeBounds, zooms, seedPurgeGrid)
 
 	return doWork(ctx, tileChannel, seedPurgeMaps, cacheConcurrency, seedPurgeWorker)
diff --git a/cmd/shigola/cmd/cache/tile_list.go b/cmd/shigola/cmd/cache/tile_list.go
index e99d82c4..5bd8d317 100644
--- a/cmd/shigola/cmd/cache/tile_list.go
+++ b/cmd/shigola/cmd/cache/tile_list.go
@@ -88,7 +88,7 @@ func tileListCommand(cmd *cobra.Command, args []string) (err error) {
 		defer tileListFile.Close()
 	}
 
-	log.Info("zoom list: ", zooms)
+	log.Info("zoom list:", zooms)
 
 	tilechannel := generateTilesForTileList(ctx, in, explicit, zooms, format)
 
diff --git a/cmd/shigola/cmd/cache/tile_name.go b/cmd/shigola/cmd/cache/tile_name.go
index 4e8a6224..0100d730 100644
--- a/cmd/shigola/cmd/cache/tile_name.go
+++ b/cmd/shigola/cmd/cache/tile_name.go
@@ -71,7 +71,7 @@ func tileNameCommand(cmd *cobra.Command, args []string) (err error) {
 		}
 	}()
 
-	log.Info("zoom list: ", zooms)
+	log.Info("zoom list:", zooms)
 	tilechannel := generateTilesForTileName(ctx, tileNameTile, explicit, zooms)
 
 	// start up workers
diff --git a/internal/log/README.md b/internal/log/README.md
index e0958c6b..f728200f 100644
--- a/internal/log/README.md
+++ b/internal/log/README.md
@@ -69,3 +69,6 @@ the call sites inherited from tegola, and log through `slog.Default()`:
 All of them attach the first non-nil `error` among their arguments under `err`,
 so `log.Errorf("tier get: %v", err)` produces both a readable message and a
 structured error. A disabled level returns before formatting anything.
+
+`fmt.Println` puts a space between every pair of operands, so a message passed to
+`Error`, `Warn`, `Info` or `Debug` should not end in one: `log.Info("zoom list:", zooms)`.
diff --git a/internal/log/format_test.go b/internal/log/format_test.go
index ad3c0f20..417a5c4b 100644
--- a/internal/log/format_test.go
+++ b/internal/log/format_test.go
@@ -236,10 +236,10 @@ func TestWrappers(t *testing.T) {
 			wantMsg: "boom",
 			wantErr: "boom",
 		},
-		// Operands are separated as Println separates them — always by a
-		// space — which reads right for the call sites that pass a message
-		// and a value, and doubles the space where the message already ends
-		// in one ("zoom list: ", zooms).
+		// Operands are separated as Println separates them, always by a
+		// space. That reads right for a message and a value, and doubles the
+		// space where the message already ends in one, which is why no call
+		// site's message does.
 		"a message and a value": {
 			emit:    func() { log.Info("zoom list:", []int{0, 1}) },
 			wantMsg: "zoom list: [0 1]",
diff --git a/internal/log/log.go b/internal/log/log.go
index 67e6c3a3..14700e01 100644
--- a/internal/log/log.go
+++ b/internal/log/log.go
@@ -292,9 +292,14 @@ func Debugf(format string, args ...any) {
 }
 
 // Error, Warn, Info and Debug format their operands as fmt.Sprintln does,
-// without the newline: the call sites were written against that
-// ("zoom list: ", zooms), and against an error on its own, which Println
-// renders as its message.
+// without the newline. The call sites pass operands — usually a message, a
+// message and a value ("zoom list:", zooms), or an error on its own, which
+// Println renders as its message. Println always separates operands with a
+// space, so a message must not end in one.
+//
+// fmt.Sprint was the other candidate, and would have spared the call sites
+// written as ("zoom list: ", zooms), but it puts no space next to a string
+// operand: ("could not purge", err) would have read "could not purgeboom".
 //
 // They used to pass args[0].(string) to slog as the message and all of args as
 // attributes, so a non-string first argument — log.Error(err) — panicked, and