diff --git a/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/execution/execution_constraints.cairo b/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/execution/execution_constraints.cairo
index e228f32b8e5..9c2fa07c6a2 100644
--- a/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/execution/execution_constraints.cairo
+++ b/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/execution/execution_constraints.cairo
@@ -11,7 +11,8 @@ from starkware.starknet.core.os.constants import (
 )
 from starkware.starknet.core.os.execution.syscall_impls import read_block_hash_from_storage
 from starkware.starknet.core.os.virtual_os_output import (
-    PROOF_VERSION,
+    PROOF_VERSION_V0,
+    PROOF_VERSION_V1,
     VIRTUAL_OS_OUTPUT_VERSION,
     VIRTUAL_SNOS,
     ProofHeader,
@@ -46,14 +47,15 @@ func check_proof_facts{range_check_ptr, contract_state_changes: DictAccess*}(
     assert_le(ProofHeader.SIZE + VirtualOsOutputHeader.SIZE, proof_facts_size);
 
     // Validate the proof header.
+    static_assert ProofHeader.SIZE == 3;
     let proof_header = cast(proof_facts, ProofHeader*);
+    assert proof_header.proof_variant = VIRTUAL_SNOS;
     assert is_program_hash_allowed(proof_header.program_hash) = TRUE;
-    // Proof version and variant are for future compatibility.
-    assert [proof_header] = ProofHeader(
-        proof_version=PROOF_VERSION,
-        proof_variant=VIRTUAL_SNOS,
-        program_hash=proof_header.program_hash,
-    );
+    // Proof version may be V0 (legacy) or V1 (current).
+    with_attr error_message("Unsupported proof version") {
+        tempvar proof_version = proof_header.proof_version;
+        assert (proof_version - PROOF_VERSION_V0) * (proof_version - PROOF_VERSION_V1) = 0;
+    }
 
     // Validate the virtual OS output header.
     let os_output_header = cast(&proof_facts[ProofHeader.SIZE], VirtualOsOutputHeader*);
diff --git a/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/virtual_os_output.cairo b/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/virtual_os_output.cairo
index 91c76c60f86..3a3b59b490e 100644
--- a/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/virtual_os_output.cairo
+++ b/crates/apollo_starknet_os_program/src/cairo/starkware/starknet/core/os/virtual_os_output.cairo
@@ -2,7 +2,10 @@
 const VIRTUAL_SNOS = 'VIRTUAL_SNOS';
 
 // Marker indicating proof facts format version 0.
-const PROOF_VERSION = 'PROOF0';
+const PROOF_VERSION_V0 = 'PROOF0';
+
+// Marker indicating proof facts format version 1.
+const PROOF_VERSION_V1 = 'PROOF1';
 
 // The version of the virtual OS output.
 //
diff --git a/crates/apollo_starknet_os_program/src/program_hash.json b/crates/apollo_starknet_os_program/src/program_hash.json
index 92413dfcd93..ad006ea8087 100644
--- a/crates/apollo_starknet_os_program/src/program_hash.json
+++ b/crates/apollo_starknet_os_program/src/program_hash.json
@@ -1,5 +1,5 @@
 {
-  "os": "0x10e4d1fd519f4675b021671fb866ec60fc0522f65273f587255414d0e5d5b23",
+  "os": "0x2a4b5650b64c1a13a4d2754353ddd85d4b970766063220253a4f96643ba23f6",
   "virtual_os": "0x39f55918423cade9e95a6a52286b56bed1c5c9b6fe39aa00301361457a3c604",
   "aggregator": "0x700786d51b3854af43d8e12180380bda3029be6c1767e007858de6ca2edac40",
   "aggregator_with_prefix": "0xe08d300e3f5996e43d6d7cc5a20068e0e58cf1309089f2348317ac580f6c1f"
diff --git a/crates/apollo_starknet_os_program/src/virtual_os_test.rs b/crates/apollo_starknet_os_program/src/virtual_os_test.rs
index 20d2737ca31..3e446bdaa78 100644
--- a/crates/apollo_starknet_os_program/src/virtual_os_test.rs
+++ b/crates/apollo_starknet_os_program/src/virtual_os_test.rs
@@ -19,7 +19,7 @@ fn test_virtual_os_swapped_files() {
 #[test]
 fn test_program_bytecode_lengths() {
     expect![[r#"
-        15660
+        15663
     "#]]
     .assert_debug_eq(&OS_PROGRAM.data_len());
     expect![[r#"
diff --git a/crates/starknet_os/src/constants_test.rs b/crates/starknet_os/src/constants_test.rs
index e5a15281586..b5fa56e4b61 100644
--- a/crates/starknet_os/src/constants_test.rs
+++ b/crates/starknet_os/src/constants_test.rs
@@ -10,6 +10,7 @@ use starknet_api::core::{
 };
 use starknet_api::transaction::fields::{
     PROOF_VERSION_V0,
+    PROOF_VERSION_V1,
     VIRTUAL_OS_OUTPUT_VERSION,
     VIRTUAL_SNOS,
 };
@@ -82,10 +83,12 @@ fn test_virtual_snos() {
     assert_eq!(Const::VirtualSnos.fetch_from_os_program().unwrap(), VIRTUAL_SNOS);
 }
 
-/// Asserts that the Rust PROOF_VERSION_V0 constant matches the Cairo constant.
+/// Asserts that the Rust PROOF_VERSION_V0 and PROOF_VERSION_V1 constants match their Cairo
+/// counterparts.
 #[test]
 fn test_proof_version() {
-    assert_eq!(Const::ProofVersion.fetch_from_os_program().unwrap(), PROOF_VERSION_V0);
+    assert_eq!(Const::ProofVersionV0.fetch_from_os_program().unwrap(), PROOF_VERSION_V0);
+    assert_eq!(Const::ProofVersionV1.fetch_from_os_program().unwrap(), PROOF_VERSION_V1);
 }
 
 /// Asserts that the Rust STARKNET_OS_CONFIG_HASH_VERSION constant matches the Cairo constant.
diff --git a/crates/starknet_os/src/hints/vars.rs b/crates/starknet_os/src/hints/vars.rs
index 17906ac9a16..e7cfcabd6d9 100644
--- a/crates/starknet_os/src/hints/vars.rs
+++ b/crates/starknet_os/src/hints/vars.rs
@@ -369,7 +369,8 @@ define_string_enum! {
             "starkware.starknet.core.os.virtual_os_output.VIRTUAL_OS_OUTPUT_VERSION"
         ),
         (VirtualSnos, "starkware.starknet.core.os.virtual_os_output.VIRTUAL_SNOS"),
-        (ProofVersion, "starkware.starknet.core.os.virtual_os_output.PROOF_VERSION"),
+        (ProofVersionV0, "starkware.starknet.core.os.virtual_os_output.PROOF_VERSION_V0"),
+        (ProofVersionV1, "starkware.starknet.core.os.virtual_os_output.PROOF_VERSION_V1"),
     }
 }