diff --git a/html/v4.0.10.html b/html/v4.0.10.html
index 83b72e0b..f1b6b008 100644
--- a/html/v4.0.10.html
+++ b/html/v4.0.10.html
@@ -144,7 +144,7 @@ information is located here:
       <TR><TD>ZIP/Deflate</TD>  <TD>1m 20 s</TD>            <TD>4.9 s </TD>               <TD>419 622 336</TD></TR>
     </TABLE>
 
-    <P>Please note that COMPRESSION_ZSTD is self-assigned the id 34926
+    <P>Please note that COMPRESSION_ZSTD is self-assigned the id 50000
     by the libtiff project and is not officially registered with Adobe
     since Adobe's registration function is defunct.</P>
   </LI>
@@ -184,7 +184,7 @@ information is located here:
 
     </TABLE>
 
-    <P>Please note that COMPRESSION_WEBP is self-assigned the id 34927
+    <P>Please note that COMPRESSION_WEBP is self-assigned the id 50001
     by the libtiff project and is not officially registered with Adobe
     since Adobe's registration function is defunct.</P>
 
diff --git a/libtiff/tiff.h b/libtiff/tiff.h
index 116ac34e..5b0a0c90 100644
--- a/libtiff/tiff.h
+++ b/libtiff/tiff.h
@@ -190,8 +190,8 @@ typedef enum {
 #define     COMPRESSION_LERC            34887   /* ESRI Lerc codec: https://github.com/Esri/lerc */
 /* compression codes 34887-34889 are reserved for ESRI */
 #define	    COMPRESSION_LZMA		34925	/* LZMA2 */
-#define	    COMPRESSION_ZSTD		34926	/* ZSTD: WARNING not registered in Adobe-maintained registry */
-#define	    COMPRESSION_WEBP		34927	/* WEBP: WARNING not registered in Adobe-maintained registry */
+#define	    COMPRESSION_ZSTD		50000	/* ZSTD: WARNING not registered in Adobe-maintained registry */
+#define	    COMPRESSION_WEBP		50001	/* WEBP: WARNING not registered in Adobe-maintained registry */
 #define	TIFFTAG_PHOTOMETRIC		262	/* photometric interpretation */
 #define	    PHOTOMETRIC_MINISWHITE	0	/* min value is white */
 #define	    PHOTOMETRIC_MINISBLACK	1	/* min value is black */