diff --git a/libavutil/opt.c b/libavutil/opt.c
index 46f60aad0e..107be6ad85 100644
--- a/libavutil/opt.c
+++ b/libavutil/opt.c
@@ -252,6 +252,21 @@ static int set_string_number(void *obj, void *target_obj, const AVOption *o, con
     return 0;
 }
 
+static int set_string_image_size(void *obj, const AVOption *o, const char *val, int *dst)
+{
+    int ret;
+
+    if (!val || !strcmp(val, "none")) {
+        dst[0] =
+        dst[1] = 0;
+        return 0;
+    }
+    ret = av_parse_video_size(dst, dst + 1, val);
+    if (ret < 0)
+        av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as image size\n", val);
+    return ret;
+}
+
 #if FF_API_OLD_AVOPTIONS
 int av_set_string3(void *obj, const char *name, const char *val, int alloc, const AVOption **o_out)
 {
@@ -286,15 +301,7 @@ int av_opt_set(void *obj, const char *name, const char *val, int search_flags)
     case AV_OPT_TYPE_FLOAT:
     case AV_OPT_TYPE_DOUBLE:
     case AV_OPT_TYPE_RATIONAL: return set_string_number(obj, target_obj, o, val, dst);
-    case AV_OPT_TYPE_IMAGE_SIZE:
-        if (!val || !strcmp(val, "none")) {
-            *(int *)dst = *((int *)dst + 1) = 0;
-            return 0;
-        }
-        ret = av_parse_video_size(dst, ((int *)dst) + 1, val);
-        if (ret < 0)
-            av_log(obj, AV_LOG_ERROR, "Unable to parse option value \"%s\" as image size\n", val);
-        return ret;
+    case AV_OPT_TYPE_IMAGE_SIZE: return set_string_image_size(obj, o, val, dst);
     case AV_OPT_TYPE_VIDEO_RATE:
         if (!val) {
             ret = AVERROR(EINVAL);