diff --git a/go/core/pkg/cli/db/migrate/migrate.go b/go/core/pkg/cli/db/migrate/migrate.go
index 57c355134..2933c4229 100644
--- a/go/core/pkg/cli/db/migrate/migrate.go
+++ b/go/core/pkg/cli/db/migrate/migrate.go
@@ -217,8 +217,8 @@ func ensureClean(src migrations.Source, mg *migrate.Migrate) error {
 	return nil
 }
 
-// sourceFileVersions returns the (ascending-sorted) NNN versions parsed from
-// every NNN_name.up.sql file in src.FS/src.Dir.
+// sourceFileVersions returns the (ascending-sorted) versions parsed from
+// every .up.sql file in src.FS/src.Dir whose filename begins with decimal digits.
 //
 // The set isn't required to be contiguous — gaps (e.g. a deleted 005) are
 // real and the missing numbers are treated as not-applicable-to-this-binary.
@@ -238,12 +238,8 @@ func sourceFileVersions(src migrations.Source) ([]int, error) {
 		if !strings.HasSuffix(name, ".up.sql") {
 			continue
 		}
-		parts := strings.SplitN(name, "_", 2)
-		if len(parts) != 2 {
-			continue
-		}
-		v, err := strconv.Atoi(parts[0])
-		if err != nil {
+		var v int
+		if _, err := fmt.Sscanf(name, "%d", &v); err != nil {
 			continue
 		}
 		versions = append(versions, v)
diff --git a/go/core/pkg/cli/db/migrate/migrate_test.go b/go/core/pkg/cli/db/migrate/migrate_test.go
index 96f802296..85c090dfa 100644
--- a/go/core/pkg/cli/db/migrate/migrate_test.go
+++ b/go/core/pkg/cli/db/migrate/migrate_test.go
@@ -362,3 +362,36 @@ func markDirty(t *testing.T, dsn, table string) {
 		t.Fatalf("mark %s dirty: %v", table, err)
 	}
 }
+
+func TestSourceFileVersions(t *testing.T) {
+	tests := []struct {
+		name  string
+		files []string
+		want  []int
+	}{
+		{"standard format", []string{"000001_create.up.sql", "000002_alter.up.sql"}, []int{1, 2}},
+		{"no underscore", []string{"000003foo.up.sql"}, []int{3}},
+		{"no leading digits ignored", []string{"notes.up.sql"}, nil},
+		{"down files ignored", []string{"000001_create.down.sql", "000001_create.up.sql"}, []int{1}},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			mfs := fstest.MapFS{}
+			for _, f := range tt.files {
+				mfs["m/"+f] = &fstest.MapFile{Data: []byte("-- sql")}
+			}
+			got, err := sourceFileVersions(migrations.Source{FS: mfs, Dir: "m"})
+			if err != nil {
+				t.Fatal(err)
+			}
+			if len(got) != len(tt.want) {
+				t.Fatalf("got %v, want %v", got, tt.want)
+			}
+			for i := range got {
+				if got[i] != tt.want[i] {
+					t.Errorf("[%d] got %d, want %d", i, got[i], tt.want[i])
+				}
+			}
+		})
+	}
+}