diff --git a/lib/msprime.c b/lib/msprime.c
index 085fe821e..229ada286 100644
--- a/lib/msprime.c
+++ b/lib/msprime.c
@@ -892,8 +892,8 @@ lineage_reset_segments(lineage_t *self)
 }
 
 static lineage_t *MSP_WARN_UNUSED
-msp_alloc_lineage(
-    msp_t *self, segment_t *head, segment_t *tail, population_id_t population, label_id_t label)
+msp_alloc_lineage(msp_t *self, segment_t *head, segment_t *tail,
+    population_id_t population, label_id_t label)
 {
     lineage_t *lin = NULL;
 
@@ -1392,7 +1392,7 @@ msp_insert_hull(msp_t *self, hull_t *hull)
     } else {
         c = avl_search_closest(hulls_right, &query, &query_node);
         /* query < node->item ==> c = -1 */
-        num_ending_before_left = (uint64_t) avl_index(query_node) + (uint64_t) (c != -1);
+        num_ending_before_left = (uint64_t) avl_index(query_node) + (uint64_t)(c != -1);
     }
     /* set number of pairs coalescing with hull */
     count = num_starting_before_left - num_ending_before_left;
@@ -1895,7 +1895,7 @@ msp_verify_non_empty_populations(msp_t *self)
 
     for (avl_node = self->non_empty_populations.head; avl_node != NULL;
          avl_node = avl_node->next) {
-        j = (tsk_id_t) (intptr_t) avl_node->item;
+        j = (tsk_id_t)(intptr_t) avl_node->item;
         tsk_bug_assert(msp_get_num_population_ancestors(self, j) > 0);
     }
 
@@ -2280,7 +2280,7 @@ msp_print_state(msp_t *self, FILE *out)
     }
     fprintf(out, "non_empty_populations = [");
     for (a = self->non_empty_populations.head; a != NULL; a = a->next) {
-        j = (uint32_t) (intptr_t) a->item;
+        j = (uint32_t)(intptr_t) a->item;
         fprintf(out, "%d,", j);
     }
     fprintf(out, "]\n");
@@ -3347,7 +3347,8 @@ msp_recombination_event(msp_t *self, label_id_t label, segment_t **lhs, segment_
     }
     tsk_bug_assert(alpha->left < alpha->right);
     msp_set_segment_mass(self, alpha);
-    right_lineage = msp_alloc_lineage(self, alpha, NULL, left_lineage->population, label);
+    right_lineage
+        = msp_alloc_lineage(self, alpha, NULL, left_lineage->population, label);
     if (right_lineage == NULL) {
         ret = MSP_ERR_NO_MEMORY;
         goto out;
@@ -3424,7 +3425,7 @@ msp_gene_conversion_event(msp_t *self, label_id_t label)
 {
     int ret = 0;
     segment_t *x, *y, *alpha, *head, *tail, *z, *new_individual_head;
-    lineage_t *new_lineage;
+    lineage_t *lineage, *new_lineage;
     double left_breakpoint, right_breakpoint, tl;
     bool insert_alpha;
     hull_t *hull = NULL;
@@ -3441,7 +3442,8 @@ msp_gene_conversion_event(msp_t *self, label_id_t label)
         goto out;
     }
 
-    population = y->lineage->population;
+    lineage = y->lineage;
+    population = lineage->population;
     x = y->prev;
 
     /* generate tract length */
@@ -3611,12 +3613,17 @@ msp_gene_conversion_event(msp_t *self, label_id_t label)
         new_individual_head = head;
     }
     if (new_individual_head != NULL) {
-        new_lineage = msp_alloc_lineage(self, new_individual_head, NULL, population, label);
+        new_lineage
+            = msp_alloc_lineage(self, new_individual_head, NULL, population, label);
         if (new_lineage == NULL) {
             ret = MSP_ERR_NO_MEMORY;
             goto out;
         }
+        lineage_reset_segments(new_lineage);
         ret = msp_insert_individual(self, new_lineage);
+        if (ret != 0) {
+            goto out;
+        }
         if (self->model.type == MSP_MODEL_SMC_K) {
             tsk_bug_assert(tract_hull_left < tract_hull_right);
             tract_hull_right = GSL_MIN(
@@ -3635,6 +3642,9 @@ msp_gene_conversion_event(msp_t *self, label_id_t label)
     } else {
         self->num_noneffective_gc_events++;
     }
+
+    lineage_reset_segments(lineage);
+
     if (self->additional_nodes & MSP_NODE_IS_GC_EVENT) {
         ret = msp_store_arg_gene_conversion(self, tail, alpha, head);
         if (ret != 0) {
@@ -4346,7 +4356,8 @@ msp_insert_root_segments(msp_t *self, const segment_t *head, segment_t **new_hea
         }
         copy->prev = prev;
         if (prev == NULL) {
-            lineage = msp_alloc_lineage(self, copy, NULL, node_population[head->value], label);
+            lineage = msp_alloc_lineage(
+                self, copy, NULL, node_population[head->value], label);
             if (lineage == NULL) {
                 ret = MSP_ERR_NO_MEMORY;
                 goto out;
@@ -5181,7 +5192,7 @@ msp_gene_conversion_left_event(msp_t *self, label_id_t label)
     double h = gsl_rng_uniform(self->rng) * gc_left_total;
     double tl, bp, lhs_old_right, lhs_new_right;
     population_id_t population;
-    lineage_t *lineage;
+    lineage_t *lineage, *new_lineage;
     segment_t *y, *x, *alpha;
     hull_t *rhs_hull;
     hull_t *lhs_hull = NULL;
@@ -5269,15 +5280,21 @@ msp_gene_conversion_left_event(msp_t *self, label_id_t label)
     }
     lhs_new_right = y->right;
 
-    lineage = msp_alloc_lineage(self, alpha, NULL, population, label);
-    if (lineage == NULL) {
+    new_lineage = msp_alloc_lineage(self, alpha, NULL, population, label);
+    if (new_lineage == NULL) {
         ret = MSP_ERR_NO_MEMORY;
         goto out;
     }
     msp_set_segment_mass(self, alpha);
     tsk_bug_assert(alpha->prev == NULL);
 
-    ret = msp_insert_individual(self, lineage);
+    lineage_reset_segments(new_lineage);
+    lineage_reset_segments(lineage);
+
+    ret = msp_insert_individual(self, new_lineage);
+    if (ret != 0) {
+        goto out;
+    }
     if (self->additional_nodes & MSP_NODE_IS_GC_EVENT) {
         ret = msp_store_arg_gene_conversion(self, NULL, y, alpha);
         if (ret != 0) {
@@ -5376,7 +5393,7 @@ msp_run_coalescent(msp_t *self, double max_time, unsigned long max_events)
         ca_pop_id = 0;
         for (avl_node = self->non_empty_populations.head; avl_node != NULL;
              avl_node = avl_node->next) {
-            pop_id = (tsk_id_t) (intptr_t) avl_node->item;
+            pop_id = (tsk_id_t)(intptr_t) avl_node->item;
             t_temp = self->get_common_ancestor_waiting_time(self, pop_id, label);
             if (t_temp < ca_t_wait) {
                 ca_t_wait = t_temp;
@@ -5390,7 +5407,7 @@ msp_run_coalescent(msp_t *self, double max_time, unsigned long max_events)
         mig_dest_pop = 0;
         for (avl_node = self->non_empty_populations.head; avl_node != NULL;
              avl_node = avl_node->next) {
-            pop_id_j = (tsk_id_t) (intptr_t) avl_node->item;
+            pop_id_j = (tsk_id_t)(intptr_t) avl_node->item;
             pop = &self->populations[pop_id_j];
             n = avl_count(&pop->ancestors[label]);
             tsk_bug_assert(n > 0);
@@ -7505,7 +7522,7 @@ msp_instantaneous_bottleneck(msp_t *self, demographic_event_t *event)
     for (u = 0; u < (tsk_id_t) n; u++) {
         lineages[u] = u;
     }
-    for (u = 0; u < (tsk_id_t) (2 * n); u++) {
+    for (u = 0; u < (tsk_id_t)(2 * n); u++) {
         pi[u] = TSK_NULL;
     }
     j = 0;
@@ -8380,7 +8397,7 @@ genic_selection_generate_trajectory(sweep_t *self, msp_t *simulator,
         alpha = 2 * pop_size * trajectory.s;
         x = 1.0
             - genic_selection_stochastic_forwards(
-                trajectory.dt, 1.0 - x, alpha, gsl_rng_uniform(rng));
+                  trajectory.dt, 1.0 - x, alpha, gsl_rng_uniform(rng));
         /* need our recored traj to stay in bounds */
         t += trajectory.dt;
         sim_time += trajectory.dt * pop_size * simulator->ploidy;
diff --git a/lib/tests/test_ancestry.c b/lib/tests/test_ancestry.c
index 11833c1a7..82de438a7 100644
--- a/lib/tests/test_ancestry.c
+++ b/lib/tests/test_ancestry.c
@@ -1297,7 +1297,7 @@ test_mixed_hudson_smc(void)
     /* Run for 1 event each for the models, interleaving */
     j = 0;
     while ((ret = msp_run(&msp, DBL_MAX, 1)) == MSP_EXIT_MAX_EVENTS) {
-        printf("X\n");
+        /* msp_print_state(&msp, stdout); */
         msp_verify(&msp, 0);
         CU_ASSERT_FALSE(msp_is_completed(&msp));
         model = msp_get_model(&msp)->type;