diff --git a/powerpc/filter_vsx_intrinsics.c b/powerpc/filter_vsx_intrinsics.c
index fe1483a13..833f9cc44 100644
--- a/powerpc/filter_vsx_intrinsics.c
+++ b/powerpc/filter_vsx_intrinsics.c
@@ -36,26 +36,37 @@ void png_read_filter_row_up_vsx(png_row_infop row_info, png_bytep row,
                                 png_const_bytep prev_row)
 {
    png_size_t i;
-   png_size_t istop = row_info->rowbytes;
+   png_size_t unaligned_top = (png_size_t)row % 16;
+   png_size_t istop = row_info->rowbytes - unaligned_top;
    png_bytep rp = row;
    png_const_bytep pp = prev_row;
 
    vector unsigned char rp_vec;
    vector unsigned char pp_vec;
 
+   /* Altivec operations require 16-byte aligned data 
+    * but input can be unaligned. So we calculate 
+    * unaligned part as usual.
+    */
+   for (i = 0; i < unaligned_top; i++)
+   {
+      *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
+      rp++;
+   }
+
    /* Using SIMD while we can */
    while( istop >= 16 )
    {
-	   rp_vec = vec_ld(0,rp);
-	   pp_vec = vec_ld(0,pp);
-	
-	   rp_vec = vec_add(rp_vec,pp_vec);
-	
-	   vec_st(rp_vec,0,rp);
+      rp_vec = vec_ld(0,rp);
+      pp_vec = vec_ld(0,pp);
+   
+      rp_vec = vec_add(rp_vec,pp_vec);
 
-	   pp += 16;
-	   rp += 16;
-	   istop -= 16;
+      vec_st(rp_vec,0,rp);
+
+      pp += 16;
+      rp += 16;
+      istop -= 16;
    }
 
    if(istop % 16 > 0)
@@ -68,10 +79,11 @@ void png_read_filter_row_up_vsx(png_row_infop row_info, png_bytep row,
          *rp = (png_byte)(((int)(*rp) + (int)(*pp++)) & 0xff);
          rp++;
       }
-   }
 }
 
-void png_read_filter_row_sub4_vsx(png_row_infop row_info, png_bytep row,
+}
+
+void png_read_filter_row_sub_vsx(png_row_infop row_info, png_bytep row,
                                   png_const_bytep prev_row)
 {
    const unsigned int bpp = 4;
@@ -88,23 +100,6 @@ void png_read_filter_row_sub4_vsx(png_row_infop row_info, png_bytep row,
    }
 }
 
-void png_read_filter_row_sub3_vsx(png_row_infop row_info, png_bytep row,
-                                  png_const_bytep prev_row)
-{
-    const unsigned int bpp = 4;
-    png_size_t i;
-    png_size_t istop = row_info->rowbytes;
-    png_bytep rp = row + bpp;
-
-    PNG_UNUSED(prev_row)
-
-    for (i = bpp; i < istop; i++)
-    {
-       *rp = (png_byte)(((int)(*rp) + (int)(*(rp-3))) & 0xff);
-       rp++;
-    }
-}
-
 void png_read_filter_row_avg4_vsx(png_row_infop row_info, png_bytep row,
                                   png_const_bytep prev_row)
 {