diff --git a/spartan/environments/testnet.env b/spartan/environments/testnet.env
index 613a48747e4f..c748a1587f4e 100644
--- a/spartan/environments/testnet.env
+++ b/spartan/environments/testnet.env
@@ -32,6 +32,19 @@ AZTEC_PROVING_COST_PER_MANA=12500000
 AZTEC_SLASH_AMOUNT_SMALL=100000e18
 AZTEC_SLASH_AMOUNT_MEDIUM=250000e18
 AZTEC_SLASH_AMOUNT_LARGE=250000e18
+# Per-offense penalties must be on the same scale as the onchain slash amounts above. The slasher sums an
+# offender's penalties for an epoch and maps the total to 1/2/3 slash units by comparing against
+# [SMALL, MEDIUM, LARGE]; a total below SMALL maps to 0 units and is never voted on. The generated defaults
+# (10e18) are ~10,000x below SMALL (100000e18), so without these overrides every offense rounds down to 0
+# units and slashing can never trigger on testnet. Liveness faults map to SMALL (1 unit); provable validity
+# and data-availability faults map to LARGE (3 units).
+SLASH_INACTIVITY_PENALTY=100000e18
+SLASH_UNKNOWN_PENALTY=100000e18
+SLASH_DATA_WITHHOLDING_PENALTY=250000e18
+SLASH_INVALID_BLOCK_PENALTY=250000e18
+SLASH_PROPOSE_INVALID_ATTESTATIONS_PENALTY=250000e18
+SLASH_PROPOSE_DESCENDANT_OF_CHECKPOINT_WITH_INVALID_ATTESTATIONS_PENALTY=250000e18
+SLASH_ATTEST_INVALID_CHECKPOINT_PROPOSAL_PENALTY=250000e18
 AZTEC_ACTIVATION_THRESHOLD=200000e18
 AZTEC_EJECTION_THRESHOLD=100000e18
 AZTEC_GOVERNANCE_PROPOSER_ROUND_SIZE=100