diff --git a/libtiff/tif_next.c b/libtiff/tif_next.c
index b014685..13c0848 100644
--- a/libtiff/tif_next.c
+++ b/libtiff/tif_next.c
@@ -37,7 +37,7 @@
 	case 0:	op[0]  = (unsigned char) ((v) << 6); break;	\
 	case 1:	op[0] |= (v) << 4; break;	\
 	case 2:	op[0] |= (v) << 2; break;	\
-	case 3:	*op++ |= (v);	   break;	\
+	case 3:	*op++ |= (v); op_offset++;   break;	\
 	}					\
 }
 
@@ -107,6 +107,8 @@ NeXTDecode(TIFF* tif, uint8* buf, tmsize_t occ, uint16 s)
             if( isTiled(tif) )
                 imagewidth = tif->tif_dir.td_tilewidth;
 
+            tmsize_t op_offset = 0;
+
 			/*
 			 * The scanline is composed of a sequence of constant
 			 * color ``runs''.  We shift into ``run mode'' and
@@ -120,10 +122,15 @@ NeXTDecode(TIFF* tif, uint8* buf, tmsize_t occ, uint16 s)
 				 * bounds, potentially resulting in a security
 				 * issue.
 				 */
-				while (n-- > 0 && npixels < imagewidth)
+				while (n-- > 0 && npixels < imagewidth && op_offset < scanline)
 					SETPIXEL(op, grey);
 				if (npixels >= imagewidth)
 					break;
+                if (op_offset >= scanline ) {
+                    TIFFErrorExt(tif->tif_clientdata, module, "Invalid data for scanline %ld",
+                            (long) tif->tif_row);
+                    return (0);
+                }
 				if (cc == 0)
 					goto bad;
 				n = *bp++, cc--;
@@ -162,9 +169,9 @@ NeXTPreDecode(TIFF* tif, uint16 s)
 TIFFInitNeXT(TIFF* tif, int scheme)
 {
 	(void) scheme;
-	tif->tif_predecode = NeXTPreDecode;
-	tif->tif_decoderow = NeXTDecode;  
-	tif->tif_decodestrip = NeXTDecode;  
+	tif->tif_predecode = NeXTPreDecode;
+	tif->tif_decoderow = NeXTDecode;
+	tif->tif_decodestrip = NeXTDecode;
 	tif->tif_decodetile = NeXTDecode;
 	return (1);
 }