diff --git a/builder/qemu/builder_test.go b/builder/qemu/builder_test.go
index d2a1d1eba9b..f885c570ba2 100644
--- a/builder/qemu/builder_test.go
+++ b/builder/qemu/builder_test.go
@@ -132,6 +132,48 @@ func TestBuilderPrepare_BootWait(t *testing.T) {
 	}
 }
 
+func TestBuilderPrepare_DiskCompaction(t *testing.T) {
+	var b Builder
+	config := testConfig()
+
+	// Bad
+	config["skip_compaction"] = false
+	config["disk_compression"] = true
+	config["format"] = "img"
+	warns, err := b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
+	if err == nil {
+		t.Fatal("should have error")
+	}
+	if b.config.SkipCompaction != true {
+		t.Fatalf("SkipCompaction should be true")
+	}
+	if b.config.DiskCompression != false {
+		t.Fatalf("DiskCompression should be false")
+	}
+
+	// Good
+	config["skip_compaction"] = false
+	config["disk_compression"] = true
+	config["format"] = "qcow2"
+	b = Builder{}
+	warns, err = b.Prepare(config)
+	if len(warns) > 0 {
+		t.Fatalf("bad: %#v", warns)
+	}
+	if err != nil {
+		t.Fatalf("should not have error: %s", err)
+	}
+	if b.config.SkipCompaction != false {
+		t.Fatalf("SkipCompaction should be false")
+	}
+	if b.config.DiskCompression != true {
+		t.Fatalf("DiskCompression should be true")
+	}
+}
+
 func TestBuilderPrepare_DiskSize(t *testing.T) {
 	var b Builder
 	config := testConfig()