diff --git a/core/load-git.c b/core/load-git.c
index 9753e0586..c44a880ae 100644
--- a/core/load-git.c
+++ b/core/load-git.c
@@ -641,6 +641,14 @@ static char *parse_sample_unit(struct sample *sample, double val, char *unit)
 	return end;
 }
 
+/*
+ * If the given cylinder doesn't exist, return NO_SENSOR.
+ */
+static uint8_t sanitize_sensor_id(const struct dive *d, int nr)
+{
+	return d && nr >= 0 && nr < d->cylinders.nr ? nr : NO_SENSOR;
+}
+
 /*
  * By default the sample data does not change unless the
  * save-file gives an explicit new value. So we copy the
@@ -667,8 +675,8 @@ static struct sample *new_sample(struct git_parser_state *state)
 		sample->pressure[0].mbar = 0;
 		sample->pressure[1].mbar = 0;
 	} else {
-		sample->sensor[0] = !state->o2pressure_sensor;
-		sample->sensor[1] = state->o2pressure_sensor;
+		sample->sensor[0] = sanitize_sensor_id(state->active_dive, !state->o2pressure_sensor);
+		sample->sensor[1] = sanitize_sensor_id(state->active_dive, state->o2pressure_sensor);
 	}
 	return sample;
 }
diff --git a/core/parse.c b/core/parse.c
index 459108a26..241d5763f 100644
--- a/core/parse.c
+++ b/core/parse.c
@@ -364,6 +364,14 @@ void ws_end(struct parser_state *state)
 {
 }
 
+/*
+ * If the given cylinder doesn't exist, return NO_SENSOR.
+ */
+static uint8_t sanitize_sensor_id(const struct dive *d, int nr)
+{
+	return d && nr >= 0 && nr < d->cylinders.nr ? nr : NO_SENSOR;
+}
+
 /*
  * By default the sample data does not change unless the
  * save-file gives an explicit new value. So we copy the
@@ -392,8 +400,8 @@ void sample_start(struct parser_state *state)
 		sample->pressure[0].mbar = 0;
 		sample->pressure[1].mbar = 0;
 	} else {
-		sample->sensor[0] = !state->o2pressure_sensor;
-		sample->sensor[1] = state->o2pressure_sensor;
+		sample->sensor[0] = sanitize_sensor_id(state->cur_dive, !state->o2pressure_sensor);
+		sample->sensor[1] = sanitize_sensor_id(state->cur_dive, state->o2pressure_sensor);
 	}
 	state->cur_sample = sample;
 	state->next_o2_sensor = 0;