diff --git a/.github/workflows/go.yaml b/.github/workflows/go.yaml
index 83d16f927c6..8b048b8dcf0 100644
--- a/.github/workflows/go.yaml
+++ b/.github/workflows/go.yaml
@@ -66,6 +66,41 @@ jobs:
       - name: Linting & vetting
         run: make go-lint
 
+  unit:
+    strategy:
+      fail-fast: false
+    runs-on: ubuntu-latest
+    name: Thanos unit tests
+    env:
+      GOBIN: /tmp/.bin
+    steps:
+      - name: Checkout code
+        uses: actions/checkout@v3
+
+      - name: Install Go.
+        uses: actions/setup-go@v3
+        with:
+          go-version: 1.21.x
+
+      - name: Install Prometheus
+        run: |
+          wget https://github.com/prometheus/prometheus/releases/download/v2.50.0/prometheus-2.50.0.linux-amd64.tar.gz
+          tar xvf prometheus-2.50.0.linux-amd64.tar.gz
+          mv prometheus-2.50.0.linux-amd64/prometheus prometheus-2.50.0.linux-amd64/prometheus-v0.37.0
+          echo prometheus-2.50.0.linux-amd64 >> $GITHUB_PATH
+
+      - uses: actions/cache@v3
+        with:
+          path: |
+            ~/.cache/go-build
+            ~/.cache/golangci-lint
+            ~/go/pkg/mod
+            ~/prometheus-2.50.0.linux-amd64
+          key: ${{ runner.os }}-go-${{ hashFiles('**/go.sum') }}
+
+      - name: Run unit tests
+        run: make test-local
+
   e2e:
     strategy:
       fail-fast: false
diff --git a/pkg/compact/compact.go b/pkg/compact/compact.go
index 454c322f495..38933bfc498 100644
--- a/pkg/compact/compact.go
+++ b/pkg/compact/compact.go
@@ -4,6 +4,7 @@
 package compact
 
 import (
+	"bytes"
 	"context"
 	"fmt"
 	"math"
@@ -1069,7 +1070,7 @@ func (cg *Group) removeOverlappingBlocks(ctx context.Context, toCompact []*metad
 	for _, m := range toCompact {
 		if m.ULID.Compare(kept.ULID) == 0 {
 			level.Info(cg.logger).Log("msg", "skip the longest overlapping block", "block", m.String(),
-				"level", m.Compaction.Level, "source", m.Thanos.Source, "labels", m.Thanos.Labels)
+				"level", m.Compaction.Level, "source", m.Thanos.Source, "labels", map2str(m.Thanos.Labels))
 			continue
 		}
 		cg.overlappingBlocks.Inc()
@@ -1078,9 +1079,17 @@ func (cg *Group) removeOverlappingBlocks(ctx context.Context, toCompact []*metad
 	return nil
 }
 
+func map2str(labels map[string]string) string {
+	b := new(bytes.Buffer)
+	for k, v := range labels {
+		fmt.Fprintf(b, "%s=%s,", k, v)
+	}
+	return b.String()
+}
+
 func DeleteBlockNow(ctx context.Context, logger log.Logger, bkt objstore.Bucket, m *metadata.Meta, dir string) error {
 	level.Warn(logger).Log("msg", "delete polluted block immediately", "block", m.String(),
-		"level", m.Compaction.Level, "source", m.Thanos.Source, "labels", m.Thanos.Labels)
+		"level", m.Compaction.Level, "source", m.Thanos.Source, "labels", map2str(m.Thanos.Labels))
 	if err := block.Delete(ctx, logger, bkt, m.ULID); err != nil {
 		return errors.Wrapf(err, "delete overlapping block %s", m.String())
 	}