diff --git a/libgnucash/engine/CMakeLists.txt b/libgnucash/engine/CMakeLists.txt
index ba85668b02..7639012ec7 100644
--- a/libgnucash/engine/CMakeLists.txt
+++ b/libgnucash/engine/CMakeLists.txt
@@ -137,7 +137,7 @@ add_custom_target(iso-4217-c DEPENDS ${ISO_4217_C})
 
 set (engine_SOURCES
   Account.cpp
-  Recurrence.c
+  Recurrence.cpp
   Query.c
   SchedXaction.c
   SX-book.c
diff --git a/libgnucash/engine/Recurrence.c b/libgnucash/engine/Recurrence.cpp
similarity index 98%
rename from libgnucash/engine/Recurrence.c
rename to libgnucash/engine/Recurrence.cpp
index f507396acf..e4f378a0c2 100644
--- a/libgnucash/engine/Recurrence.c
+++ b/libgnucash/engine/Recurrence.cpp
@@ -41,12 +41,12 @@ static QofLogModule log_module = LOG_MOD;
 static GDate invalid_gdate;
 
 /* Do not intl. These are used for xml storage. */
-static gchar *period_type_strings[NUM_PERIOD_TYPES] =
+static const gchar *period_type_strings[NUM_PERIOD_TYPES] =
 {
     "once", "day", "week", "month", "end of month",
     "nth weekday", "last weekday", "year",
 };
-static gchar *weekend_adj_strings[NUM_WEEKEND_ADJS] =
+static const gchar *weekend_adj_strings[NUM_WEEKEND_ADJS] =
 {
     "none", "back", "forward",
 };
@@ -447,7 +447,7 @@ recurrenceListNextInstance(const GList *rlist, const GDate *ref, GDate *next)
 
     for (iter = rlist; iter; iter = iter->next)
     {
-        const Recurrence *r = iter->data;
+        auto r = static_cast<const Recurrence *>(iter->data);
 
         recurrenceNextInstance(r, ref, &nextSingle);
         if (!g_date_valid(&nextSingle)) continue;
@@ -463,8 +463,8 @@ recurrenceListNextInstance(const GList *rlist, const GDate *ref, GDate *next)
 gchar *
 recurrenceToString(const Recurrence *r)
 {
-    gchar *tmpDate;
-    gchar *tmpPeriod, *ret;
+    gchar *tmpDate, *ret;
+    const gchar *tmpPeriod;
 
     g_return_val_if_fail(g_date_valid(&r->start), NULL);
     tmpDate = g_new0(gchar, MAX_DATE_LENGTH + 1);
@@ -531,8 +531,8 @@ recurrencePeriodTypeFromString(const gchar *str)
 
     for (i = 0; i < NUM_PERIOD_TYPES; i++)
         if (g_strcmp0(period_type_strings[i], str) == 0)
-            return i;
-    return -1;
+            return static_cast<PeriodType>(i);
+    return static_cast<PeriodType>(-1);
 }
 
 const gchar *
@@ -548,8 +548,8 @@ recurrenceWeekendAdjustFromString(const gchar *str)
 
     for (i = 0; i < NUM_WEEKEND_ADJS; i++)
         if (g_strcmp0(weekend_adj_strings[i], str) == 0)
-            return i;
-    return -1;
+            return static_cast<WeekendAdjust>(i);
+    return static_cast<WeekendAdjust>(-1);
 }
 
 gboolean
diff --git a/po/POTFILES.in b/po/POTFILES.in
index 0bf47323ed..6370bf2da4 100644
--- a/po/POTFILES.in
+++ b/po/POTFILES.in
@@ -683,7 +683,7 @@ libgnucash/engine/qof-string-cache.cpp
 libgnucash/engine/qofutil.cpp
 libgnucash/engine/qof-win32.cpp
 libgnucash/engine/Query.c
-libgnucash/engine/Recurrence.c
+libgnucash/engine/Recurrence.cpp
 libgnucash/engine/SchedXaction.c
 libgnucash/engine/Scrub2.c
 libgnucash/engine/Scrub3.c