diff --git a/oscar/Graphs/gLineChart.cpp b/oscar/Graphs/gLineChart.cpp
index 19ee86f5..751691bf 100644
--- a/oscar/Graphs/gLineChart.cpp
+++ b/oscar/Graphs/gLineChart.cpp
@@ -116,7 +116,9 @@ void gLineChart::SetDay(Day *d)
             Session *sess = d->sessions[i];
             if (!sess->enabled()) continue;
 
-            CPAPMode mode = (CPAPMode)sess->settings[CPAP_Mode].toInt();
+            // Don't use operator[] here or else it will insert a default-constructed entry
+            // into sess->settings if it's not present.
+            CPAPMode mode = (CPAPMode)sess->settings.value(CPAP_Mode).toInt();
 
             if (mode >= MODE_BILEVEL_FIXED) {
                 m_enabled[CPAP_Pressure] = true;    // probably a confusion of Pressure and IPAP somewhere
diff --git a/oscar/SleepLib/day.cpp b/oscar/SleepLib/day.cpp
index bc386795..6f140f96 100644
--- a/oscar/SleepLib/day.cpp
+++ b/oscar/SleepLib/day.cpp
@@ -304,10 +304,17 @@ EventDataType Day::settings_wavg(ChannelID code)
     double s0 = 0, s1 = 0, s2 = 0, tmp;
 
     for (auto & sess : sessions) {
-        if (sess->enabled() && sess->type() == MT_CPAP) {
+        if (sess->enabled()) {
             auto set = sess->settings.find(code);
 
             if (set != sess->settings.end()) {
+                if (code == CPAP_Mode && sess->type() != MT_CPAP) {
+                    // There used to be a bug in gLineChart::SetDay that inserted a CPAP_Mode
+                    // setting in any session that didn't already have one. That shouldn't
+                    // happen any more, but leave this diagnostic message here in case it does.
+                    qWarning() << sess->session() << "non-CPAP session with CPAP mode setting";
+                    continue;
+                }
                 s0 = sess->hours();
                 tmp = set.value().toDouble();
                 s1 += tmp * s0;