diff --git a/quic/core/crypto/cert_compressor.cc b/quic/core/crypto/cert_compressor.cc
index e2a352d..1fdc3ba 100644
--- a/quic/core/crypto/cert_compressor.cc
+++ b/quic/core/crypto/cert_compressor.cc
@@ -11,6 +11,7 @@
 
 #include "absl/strings/string_view.h"
 #include "quic/core/quic_utils.h"
+#include "quic/platform/api/quic_bug_tracker.h"
 #include "third_party/zlib/zlib.h"
 
 namespace quic {
@@ -215,8 +216,11 @@
       }
     }
 
-    if (common_sets && common_sets->MatchCert(*i, client_common_set_hashes,
-                                              &entry.set_hash, &entry.index)) {
+    if (GetQuicRestartFlag(quic_no_common_cert_set)) {
+      QUIC_RESTART_FLAG_COUNT(quic_no_common_cert_set);
+    } else if (common_sets &&
+               common_sets->MatchCert(*i, client_common_set_hashes,
+                                      &entry.set_hash, &entry.index)) {
       entry.type = CertEntry::COMMON;
       entries.push_back(entry);
       continue;
@@ -243,6 +247,8 @@
         entries_size += sizeof(uint64_t);
         break;
       case CertEntry::COMMON:
+        QUIC_BUG_IF(unexpected_common_cert_entry_1,
+                    GetQuicRestartFlag(quic_no_common_cert_set));
         entries_size += sizeof(uint64_t) + sizeof(uint32_t);
         break;
     }
@@ -266,6 +272,8 @@
         out += sizeof(uint64_t);
         break;
       case CertEntry::COMMON:
+        QUIC_BUG_IF(unexpected_common_cert_entry_2,
+                    GetQuicRestartFlag(quic_no_common_cert_set));
         // Assumes a little-endian machine.
         memcpy(out, &i->set_hash, sizeof(i->set_hash));
         out += sizeof(i->set_hash);
@@ -382,6 +390,10 @@
         break;
       }
       case CertEntry::COMMON: {
+        if (GetQuicRestartFlag(quic_no_common_cert_set)) {
+          // Client only. No flag count.
+          return false;
+        }
         if (!common_sets) {
           return false;
         }
@@ -628,7 +640,10 @@
         uncompressed.remove_prefix(cert_len);
         break;
       case CertEntry::CACHED:
+        break;
       case CertEntry::COMMON:
+        QUIC_BUG_IF(unexpected_common_cert_entry_3,
+                    GetQuicRestartFlag(quic_no_common_cert_set));
         break;
     }
   }
diff --git a/quic/core/crypto/cert_compressor_test.cc b/quic/core/crypto/cert_compressor_test.cc
index a024d13..f4ac507 100644
--- a/quic/core/crypto/cert_compressor_test.cc
+++ b/quic/core/crypto/cert_compressor_test.cc
@@ -56,12 +56,18 @@
       absl::string_view(reinterpret_cast<const char*>(&set_hash),
                         sizeof(set_hash)),
       absl::string_view(), common_sets.get());
-  EXPECT_EQ(
-      "03"               /* common */
-      "2a00000000000000" /* set hash 42 */
-      "01000000"         /* index 1 */
-      "00" /* end of list */,
-      absl::BytesToHexString(compressed));
+  if (!GetQuicRestartFlag(quic_no_common_cert_set)) {
+    EXPECT_EQ(
+        "03"               /* common */
+        "2a00000000000000" /* set hash 42 */
+        "01000000"         /* index 1 */
+        "00" /* end of list */,
+        absl::BytesToHexString(compressed));
+  } else {
+    ASSERT_GE(compressed.size(), 2u);
+    // 01 is the prefix for a zlib "compressed" cert not common or cached.
+    EXPECT_EQ("0100", absl::BytesToHexString(compressed.substr(0, 2)));
+  }
 
   std::vector<std::string> chain2, cached_certs;
   ASSERT_TRUE(CertCompressor::DecompressChain(compressed, cached_certs,
diff --git a/quic/core/crypto/quic_crypto_client_config.cc b/quic/core/crypto/quic_crypto_client_config.cc
index 6ecf0e8..e4989bc 100644
--- a/quic/core/crypto/quic_crypto_client_config.cc
+++ b/quic/core/crypto/quic_crypto_client_config.cc
@@ -439,7 +439,9 @@
 
   out->SetVector(kPDMD, QuicTagVector{kX509});
 
-  if (common_cert_sets) {
+  if (GetQuicRestartFlag(quic_no_common_cert_set)) {
+    // Client only. No flag count.
+  } else if (common_cert_sets) {
     out->SetStringPiece(kCCS, common_cert_sets->GetCommonHashes());
   }
 
diff --git a/quic/core/quic_flags_list.h b/quic/core/quic_flags_list.h
index 513d376..c75f37b 100644
--- a/quic/core/quic_flags_list.h
+++ b/quic/core/quic_flags_list.h
@@ -73,6 +73,8 @@
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_count_bytes_on_alternative_path_seperately, true)
 // If true, do not re-arm PTO while sending application data during handshake.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_donot_rearm_pto_on_application_data_during_handshake, true)
+// If true, do not use the gQUIC common certificate set for certificate compression.
+QUIC_FLAG(FLAGS_quic_restart_flag_quic_no_common_cert_set, false)
 // If true, drop unsent PATH_RESPONSEs and rely on peer\'s retry.
 QUIC_FLAG(FLAGS_quic_reloadable_flag_quic_drop_unsent_path_response, true)
 // If true, enable server retransmittable on wire PING.