diff --git a/main.go b/main.go
index 8881201..e211cb2 100644
--- a/main.go
+++ b/main.go
@@ -5,6 +5,7 @@ import (
 	"fmt"
 	"os"
 	"sort"
+	"strings"
 	"time"
 )
 
@@ -219,47 +220,52 @@ func Conv(name string) {
 			adjclose[k], vol))
 	}
 	if dividends != nil {
-		out, err = os.Create(name + "-dividend.csv")
-		if err != nil {
-			fmt.Printf("%s: %s\n", name, err)
-			os.Exit(-1)
-		}
-
-		defer out.Close()
-
-		out.WriteString("Date,Dividends\n")
-		for _, r := range eventRows(name, "dividend", dividends, loc) {
-			out.WriteString(fmt.Sprintf("%s,%f\n", r.date, r.amount))
-		}
+		writeEvents(name, name+"-dividend.csv", "Date,Dividends",
+			eventRows(name, "dividend", dividends, loc),
+			func(r eventRow) string { return fmt.Sprintf("%s,%f", r.date, r.amount) })
 	}
 
 	if capgains != nil {
-		out, err = os.Create(name + "-capitalGain.csv")
-		if err != nil {
-			fmt.Printf("%s: %s\n", name, err)
-			os.Exit(-1)
-		}
-
-		defer out.Close()
-
-		out.WriteString("Date,Capital Gains\n")
-		for _, r := range eventRows(name, "capital gain", capgains, loc) {
-			out.WriteString(fmt.Sprintf("%s,%f\n", r.date, r.amount))
-		}
+		writeEvents(name, name+"-capitalGain.csv", "Date,Capital Gains",
+			eventRows(name, "capital gain", capgains, loc),
+			func(r eventRow) string { return fmt.Sprintf("%s,%f", r.date, r.amount) })
 	}
 
 	if splits != nil {
-		out, err = os.Create(name + "-split.csv")
-		if err != nil {
-			fmt.Printf("%s: %s\n", name, err)
-			os.Exit(-1)
-		}
-
-		defer out.Close()
-
-		out.WriteString("Date,Stock Splits\n")
-		for _, r := range eventRows(name, "split", splits, loc) {
-			out.WriteString(fmt.Sprintf("%s,%s\n", r.date, r.ratio))
-		}
+		writeEvents(name, name+"-split.csv", "Date,Stock Splits",
+			eventRows(name, "split", splits, loc),
+			func(r eventRow) string { return fmt.Sprintf("%s,%s", r.date, r.ratio) })
+	}
+}
+
+// fileHasDataRows reports whether path exists and has a row beyond the header.
+func fileHasDataRows(path string) bool {
+	b, err := os.ReadFile(path)
+	if err != nil {
+		return false
+	}
+	lines := strings.Split(strings.TrimSpace(string(b)), "\n")
+	return len(lines) > 1 && strings.TrimSpace(lines[1]) != ""
+}
+
+// writeEvents writes the event rows to path, unless the download carries no
+// rows of this kind while an existing populated file is present: Yahoo has
+// stopped returning capitalGain events for some funds (2026), and a blind
+// overwrite would wipe the only copy of that history. (The consumer side,
+// gmp/f data.py, additionally falls back to a backup directory.)
+func writeEvents(name, path, header string, rows []eventRow, format func(eventRow) string) {
+	if len(rows) == 0 && fileHasDataRows(path) {
+		fmt.Printf("%s: no %s events in download; keeping existing %s\n", name, header, path)
+		return
+	}
+	out, err := os.Create(path)
+	if err != nil {
+		fmt.Printf("%s: %s\n", name, err)
+		os.Exit(-1)
+	}
+	defer out.Close()
+	out.WriteString(header + "\n")
+	for _, r := range rows {
+		out.WriteString(format(r) + "\n")
 	}
 }