diff --git a/Source/DOH/base.c b/Source/DOH/base.c
index 36ceb7ae3..cfbd2bdc4 100644
--- a/Source/DOH/base.c
+++ b/Source/DOH/base.c
@@ -645,7 +645,7 @@ int DohRead(DOH *obj, void *buffer, int length) {
  * DohWrite()
  * ----------------------------------------------------------------------------- */
 
-int DohWrite(DOH *obj, void *buffer, int length) {
+int DohWrite(DOH *obj, const void *buffer, int length) {
   DohBase *b = (DohBase *) obj;
   DohObjInfo *objinfo;
   if (DohCheck(obj)) {
diff --git a/Source/DOH/doh.h b/Source/DOH/doh.h
index 1ed196058..e46d103de 100644
--- a/Source/DOH/doh.h
+++ b/Source/DOH/doh.h
@@ -221,7 +221,7 @@ extern int DohDelslice(DOH *obj, int sindex, int eindex);
 
 /* File methods */
 
-extern int DohWrite(DOHFile * obj, void *buffer, int length);
+extern int DohWrite(DOHFile * obj, const void *buffer, int length);
 extern int DohRead(DOHFile * obj, void *buffer, int length);
 extern int DohSeek(DOHFile * obj, long offset, int whence);
 extern long DohTell(DOHFile * obj);
diff --git a/Source/DOH/dohint.h b/Source/DOH/dohint.h
index 661bed075..3d812b849 100644
--- a/Source/DOH/dohint.h
+++ b/Source/DOH/dohint.h
@@ -43,7 +43,7 @@ typedef struct {
 /* File methods */
 typedef struct {
   int (*doh_read) (DOH *obj, void *buffer, int nbytes);	/* Read bytes */
-  int (*doh_write) (DOH *obj, void *buffer, int nbytes);	/* Write bytes */
+  int (*doh_write) (DOH *obj, const void *buffer, int nbytes);	/* Write bytes */
   int (*doh_putc) (DOH *obj, int ch);	/* Put character */
   int (*doh_getc) (DOH *obj);	/* Get character */
   int (*doh_ungetc) (DOH *obj, int ch);	/* Unget character */
diff --git a/Source/DOH/file.c b/Source/DOH/file.c
index a9ee332bf..11482fa7f 100644
--- a/Source/DOH/file.c
+++ b/Source/DOH/file.c
@@ -67,7 +67,7 @@ static int File_read(DOH *fo, void *buffer, int len) {
  * File_write()
  * ----------------------------------------------------------------------------- */
 
-static int File_write(DOH *fo, void *buffer, int len) {
+static int File_write(DOH *fo, const void *buffer, int len) {
   DohFile *f = (DohFile *) ObjData(fo);
   if (f->filep) {
     int ret = (int) fwrite(buffer, 1, len, f->filep);
diff --git a/Source/DOH/string.c b/Source/DOH/string.c
index bd36c4094..05ae6e963 100644
--- a/Source/DOH/string.c
+++ b/Source/DOH/string.c
@@ -419,7 +419,7 @@ static int String_read(DOH *so, void *buffer, int len) {
 /* -----------------------------------------------------------------------------
  * int String_write() - Write data to a string
  * ----------------------------------------------------------------------------- */
-static int String_write(DOH *so, void *buffer, int len) {
+static int String_write(DOH *so, const void *buffer, int len) {
   int newlen;
   String *s = (String *) ObjData(so);
   s->hashkey = -1;