diff --git a/webif/lib/ts.class b/webif/lib/ts.class
index 34087cf..de18178 100644
--- a/webif/lib/ts.class
+++ b/webif/lib/ts.class
@@ -354,13 +354,14 @@ ts method mkbmps {{offset 0}} {
 
 ts method mkbmp {{offset 0} {ext ""}} {
 	set bfile [file rootname $file]
-	set cmd [list /mod/bin/ffmpeg -loglevel fatal -ss $offset -i $file \
-	    -frames 1 -pix_fmt argb -vf vflip -s 140x78 "$bfile$ext.bmp"]
-	if {[catch { exec {*}$cmd } msg]} {
-		puts "ERROR: $msg"
-		return 0
-	}
-	return 1
+    set bmpfile "$bfile$ext.bmp"
+    set cmd [list /mod/bin/ffmpeg -loglevel fatal -ss $offset -i $file \
+        -frames 1 -pix_fmt argb -vf vflip -s 140x78 -y $bmpfile]
+    catch { exec {*}$cmd }
+    if {![catch { file stat $bmpfile stbmp }]} {
+            if {[dict get $stbmp size] != 0} { return 1 }
+    }
+    return 0
 }
 
 ts method mkthm {{offset 0}} {