diff --git a/common/database/sqlite_dsn.go b/common/database/sqlite_dsn.go
index 7da673ee..7f28e5bd 100644
--- a/common/database/sqlite_dsn.go
+++ b/common/database/sqlite_dsn.go
@@ -30,10 +30,9 @@ var sqlitePragmas = [][2]string{
 }
 
 // sqliteDSN returns source with the defaults in sqlitePragmas added.
-// In-memory databases are returned untouched: WAL has no meaning there, and
-// every connection to one is its own database anyway.
+// In-memory databases are returned untouched: WAL has no meaning there.
 func sqliteDSN(source string) string {
-	if source == "" || strings.Contains(source, ":memory:") || strings.Contains(source, "mode=memory") {
+	if source == "" {
 		return source
 	}
 
@@ -46,6 +45,9 @@ func sqliteDSN(source string) string {
 		// Not something to rewrite blind; the driver will report it.
 		return source
 	}
+	if isMemoryDB(path, q) {
+		return source
+	}
 	for _, p := range sqlitePragmas {
 		if _, set := q[p[0]]; !set {
 			q.Set(p[0], p[1])
@@ -54,6 +56,17 @@ func sqliteDSN(source string) string {
 	return path + "?" + q.Encode()
 }
 
+// isMemoryDB reports whether the source names an in-memory database: the exact
+// filename forms sqlite recognises, or a mode=memory parameter. A file that
+// merely has ":memory:" or "mode=memory" somewhere in its name is a file.
+func isMemoryDB(path string, q url.Values) bool {
+	switch path {
+	case ":memory:", "file::memory:", "file:":
+		return true
+	}
+	return q.Get("mode") == "memory"
+}
+
 // withSqliteDefaults wraps open so every connection string handed to a sqlite3
 // dialector - the primary and any replicas - carries the defaults above.
 func withSqliteDefaults(driver string, open func(string) gorm.Dialector) func(string) gorm.Dialector {
diff --git a/common/database/sqlite_dsn_test.go b/common/database/sqlite_dsn_test.go
index e4da5ff4..35def066 100644
--- a/common/database/sqlite_dsn_test.go
+++ b/common/database/sqlite_dsn_test.go
@@ -36,6 +36,14 @@ func TestSqliteDSN(t *testing.T) {
 		}
 	})
 
+	t.Run("files that only look like memory databases get the defaults", func(t *testing.T) {
+		for _, s := range []string{"mode=memory.db", "/tmp/:memory:.db", "data/mode=memory/app.db"} {
+			if got := sqliteDSN(s); got == s {
+				t.Errorf("sqliteDSN(%q) was left untouched", s)
+			}
+		}
+	})
+
 	t.Run("in-memory and empty untouched", func(t *testing.T) {
 		for _, s := range []string{"", ":memory:", "file::memory:?cache=shared", "file:x?mode=memory"} {
 			if got := sqliteDSN(s); got != s {