diff --git a/harness/src/fuzz/firedancer.rs b/harness/src/fuzz/firedancer.rs
index bdf77f05..dee98721 100644
--- a/harness/src/fuzz/firedancer.rs
+++ b/harness/src/fuzz/firedancer.rs
@@ -8,7 +8,6 @@ use {
     crate::{
         accounts::{compile_accounts, CompiledAccounts},
         result::{Check, InstructionResult},
-        sysvar::Sysvars,
         Mollusk, DEFAULT_LOADER_KEY,
     },
     mollusk_svm_fuzz_fixture_firedancer::{
@@ -136,7 +135,6 @@ fn parse_fixture_context(
     let mollusk = Mollusk {
         compute_budget,
         feature_set: epoch_context.feature_set.clone(),
-        sysvars: Sysvars::fill_from_accounts(&accounts),
         ..Default::default()
     };
 
diff --git a/harness/src/lib.rs b/harness/src/lib.rs
index 5fa5102d..ab808f89 100644
--- a/harness/src/lib.rs
+++ b/harness/src/lib.rs
@@ -44,10 +44,7 @@ use {
     accounts::CompiledAccounts,
     mollusk_svm_error::error::{MolluskError, MolluskPanic},
     solana_compute_budget::compute_budget::ComputeBudget,
-    solana_program_runtime::{
-        invoke_context::{EnvironmentConfig, InvokeContext},
-        sysvar_cache::SysvarCache,
-    },
+    solana_program_runtime::invoke_context::{EnvironmentConfig, InvokeContext},
     solana_sdk::{
         account::AccountSharedData, bpf_loader_upgradeable, feature_set::FeatureSet,
         fee::FeeStructure, hash::Hash, instruction::Instruction, pubkey::Pubkey,
@@ -175,17 +172,18 @@ impl Mollusk {
         );
 
         let invoke_result = {
-            let mut cache = self.program_cache.cache().write().unwrap();
+            let mut program_cache = self.program_cache.cache().write().unwrap();
+            let sysvar_cache = self.sysvars.setup_sysvar_cache(accounts);
             InvokeContext::new(
                 &mut transaction_context,
-                &mut cache,
+                &mut program_cache,
                 EnvironmentConfig::new(
                     Hash::default(),
                     None,
                     None,
                     Arc::new(self.feature_set.clone()),
                     self.fee_structure.lamports_per_signature,
-                    &SysvarCache::from(&self.sysvars),
+                    &sysvar_cache,
                 ),
                 None,
                 self.compute_budget,
diff --git a/harness/src/sysvar.rs b/harness/src/sysvar.rs
index 4fd6a544..9972a2b2 100644
--- a/harness/src/sysvar.rs
+++ b/harness/src/sysvar.rs
@@ -59,36 +59,6 @@ impl Default for Sysvars {
 }
 
 impl Sysvars {
-    /// Create a `Sysvars` instance from a list of accounts. Any missing
-    /// sysvars will be filled with default values.
-    pub fn fill_from_accounts(accounts: &[(Pubkey, AccountSharedData)]) -> Self {
-        let mut me = Self::default();
-        for (key, account) in accounts {
-            if key == &Clock::id() {
-                me.clock = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &EpochRewards::id() {
-                me.epoch_rewards = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &EpochSchedule::id() {
-                me.epoch_schedule = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &LastRestartSlot::id() {
-                me.last_restart_slot = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &Rent::id() {
-                me.rent = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &SlotHashes::id() {
-                me.slot_hashes = bincode::deserialize(account.data()).unwrap();
-            }
-            if key == &StakeHistory::id() {
-                me.stake_history = bincode::deserialize(account.data()).unwrap();
-            }
-        }
-        me
-    }
-
     fn sysvar_account<T: SysvarId + Sysvar>(&self, sysvar: &T) -> (Pubkey, AccountSharedData) {
         let data = bincode::serialize::<T>(sysvar).unwrap();
         let space = data.len();
@@ -172,6 +142,47 @@ impl Sysvars {
             }
         }
     }
+
+    pub(crate) fn setup_sysvar_cache(
+        &self,
+        accounts: &[(Pubkey, AccountSharedData)],
+    ) -> SysvarCache {
+        let mut sysvar_cache = SysvarCache::default();
+
+        // First fill any sysvar cache entries from the provided accounts.
+        sysvar_cache.fill_missing_entries(|pubkey, set_sysvar| {
+            if let Some((_, account)) = accounts.iter().find(|(key, _)| key == pubkey) {
+                set_sysvar(account.data())
+            }
+        });
+
+        // Then fill the rest with the entries from `self`.
+        sysvar_cache.fill_missing_entries(|pubkey, set_sysvar| {
+            if pubkey.eq(&Clock::id()) {
+                set_sysvar(&bincode::serialize(&self.clock).unwrap());
+            }
+            if pubkey.eq(&EpochRewards::id()) {
+                set_sysvar(&bincode::serialize(&self.epoch_rewards).unwrap());
+            }
+            if pubkey.eq(&EpochSchedule::id()) {
+                set_sysvar(&bincode::serialize(&self.epoch_schedule).unwrap());
+            }
+            if pubkey.eq(&LastRestartSlot::id()) {
+                set_sysvar(&bincode::serialize(&self.last_restart_slot).unwrap());
+            }
+            if pubkey.eq(&Rent::id()) {
+                set_sysvar(&bincode::serialize(&self.rent).unwrap());
+            }
+            if pubkey.eq(&SlotHashes::id()) {
+                set_sysvar(&bincode::serialize(&self.slot_hashes).unwrap());
+            }
+            if pubkey.eq(&StakeHistory::id()) {
+                set_sysvar(&bincode::serialize(&self.stake_history).unwrap());
+            }
+        });
+
+        sysvar_cache
+    }
 }
 
 impl From<&Sysvars> for SysvarCache {