diff --git a/x/mock/simulation/random_simulate_blocks.go b/x/mock/simulation/random_simulate_blocks.go
index 5b1d4030c902..adeec4163deb 100644
--- a/x/mock/simulation/random_simulate_blocks.go
+++ b/x/mock/simulation/random_simulate_blocks.go
@@ -67,14 +67,16 @@ func SimulateFromSeed(
 	header := abci.Header{Height: 0, Time: timestamp}
 	opCount := 0
 
-	request := abci.RequestBeginBlock{Header: header}
-
 	var pastTimes []time.Time
+	var pastSigningValidators [][]abci.SigningValidator
+
+	request := RandomRequestBeginBlock(t, r, validators, livenessTransitionMatrix, evidenceFraction, pastTimes, pastSigningValidators, event, header, log)
 
 	for i := 0; i < numBlocks; i++ {
 
 		// Log the header time for future lookup
 		pastTimes = append(pastTimes, header.Time)
+		pastSigningValidators = append(pastSigningValidators, request.LastCommitInfo.Validators)
 
 		// Run the BeginBlock handler
 		app.BeginBlock(request)
@@ -124,7 +126,7 @@ func SimulateFromSeed(
 		}
 
 		// Generate a random RequestBeginBlock with the current validator set for the next block
-		request = RandomRequestBeginBlock(t, r, validators, livenessTransitionMatrix, evidenceFraction, pastTimes, event, header, log)
+		request = RandomRequestBeginBlock(t, r, validators, livenessTransitionMatrix, evidenceFraction, pastTimes, pastSigningValidators, event, header, log)
 
 		// Update the validator set
 		validators = updateValidators(t, r, validators, res.ValidatorUpdates, event)
@@ -147,13 +149,12 @@ func getKeys(validators map[string]mockValidator) []string {
 
 // RandomRequestBeginBlock generates a list of signing validators according to the provided list of validators, signing fraction, and evidence fraction
 func RandomRequestBeginBlock(t *testing.T, r *rand.Rand, validators map[string]mockValidator, livenessTransitions TransitionMatrix, evidenceFraction float64,
-	pastTimes []time.Time, event func(string), header abci.Header, log string) abci.RequestBeginBlock {
+	pastTimes []time.Time, pastSigningValidators [][]abci.SigningValidator, event func(string), header abci.Header, log string) abci.RequestBeginBlock {
 	if len(validators) == 0 {
 		return abci.RequestBeginBlock{Header: header}
 	}
 	signingValidators := make([]abci.SigningValidator, len(validators))
 	i := 0
-
 	for _, key := range getKeys(validators) {
 		mVal := validators[key]
 		mVal.livenessState = livenessTransitions.NextState(r, mVal.livenessState)
@@ -180,26 +181,30 @@ func RandomRequestBeginBlock(t *testing.T, r *rand.Rand, validators map[string]m
 		i++
 	}
 	evidence := make([]abci.Evidence, 0)
-	for r.Float64() < evidenceFraction {
-		height := header.Height
-		time := header.Time
-		if r.Float64() < pastEvidenceFraction {
-			height = int64(r.Intn(int(header.Height)))
-			time = pastTimes[height]
-		}
-		validator := signingValidators[r.Intn(len(signingValidators))].Validator
-		var currentTotalVotingPower int64
-		for _, mVal := range validators {
-			currentTotalVotingPower += mVal.val.Power
+	// Anything but the first block
+	if len(pastTimes) > 0 {
+		for r.Float64() < evidenceFraction {
+			height := header.Height
+			time := header.Time
+			if r.Float64() < pastEvidenceFraction {
+				height = int64(r.Intn(int(header.Height)))
+				time = pastTimes[height]
+			}
+			past := pastSigningValidators[height]
+			validator := past[r.Intn(len(past))].Validator
+			var totalVotingPower int64
+			for _, val := range past {
+				totalVotingPower += val.Validator.Power
+			}
+			evidence = append(evidence, abci.Evidence{
+				Type:             tmtypes.ABCIEvidenceTypeDuplicateVote,
+				Validator:        validator,
+				Height:           height,
+				Time:             time,
+				TotalVotingPower: totalVotingPower,
+			})
+			event("beginblock/evidence")
 		}
-		evidence = append(evidence, abci.Evidence{
-			Type:             tmtypes.ABCIEvidenceTypeDuplicateVote,
-			Validator:        validator,
-			Height:           height,
-			Time:             time,
-			TotalVotingPower: currentTotalVotingPower,
-		})
-		event("beginblock/evidence")
 	}
 	return abci.RequestBeginBlock{
 		Header: header,
diff --git a/x/slashing/slashing_period.go b/x/slashing/slashing_period.go
index 528120f0f2fc..0e5806aee97b 100644
--- a/x/slashing/slashing_period.go
+++ b/x/slashing/slashing_period.go
@@ -35,8 +35,8 @@ func (k Keeper) getValidatorSlashingPeriodForHeight(ctx sdk.Context, address sdk
 		panic("expected to find slashing period, but none was found")
 	}
 	slashingPeriod = k.unmarshalSlashingPeriodKeyValue(iterator.Key(), iterator.Value())
-	if slashingPeriod.EndHeight < height {
-		panic("slashing period ended before infraction")
+	if slashingPeriod.EndHeight > 0 && slashingPeriod.EndHeight < height {
+		panic(fmt.Sprintf("slashing period ended before infraction: infraction height %d, slashing period ended at %d", height, slashingPeriod.EndHeight))
 	}
 	return
 }