diff --git a/pngpread.c b/pngpread.c
index c12743515..1cb036db7 100644
--- a/pngpread.c
+++ b/pngpread.c
@@ -1110,11 +1110,12 @@ png_read_push_finish_row(png_structp png_ptr)
    if (png_ptr->row_number < png_ptr->num_rows)
       return;
 
+   png_ptr->old_prev_row_size = 0;   /* Force prev_row to be cleared */
+
+#if defined(PNG_READ_INTERLACING_SUPPORTED)
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
-      png_memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
-
       do
       {
          png_ptr->pass++;
@@ -1147,6 +1148,7 @@ png_read_push_finish_row(png_structp png_ptr)
 
       } while (png_ptr->iwidth == 0 || png_ptr->num_rows == 0);
    }
+#endif /* PNG_READ_INTERLACING_SUPPORTED */
 }
 
 #if defined(PNG_READ_tEXt_SUPPORTED)
diff --git a/pngrutil.c b/pngrutil.c
index d039e1161..bbc6a91f4 100644
--- a/pngrutil.c
+++ b/pngrutil.c
@@ -2992,11 +2992,12 @@ png_read_finish_row(png_structp png_ptr)
    if (png_ptr->row_number < png_ptr->num_rows)
       return;
 
+   png_ptr->old_prev_row_size = 0;   /* Force prev_row to be cleared */
+
 #ifdef PNG_READ_INTERLACING_SUPPORTED
    if (png_ptr->interlaced)
    {
       png_ptr->row_number = 0;
-      png_memset(png_ptr->prev_row, 0, png_ptr->rowbytes + 1);
       do
       {
          png_ptr->pass++;