diff --git a/src/sds.c b/src/sds.c
index bc6aa6b2f..ca915daf8 100644
--- a/src/sds.c
+++ b/src/sds.c
@@ -179,7 +179,7 @@ sds sdsgrowzero(sds s, size_t len) {
     return s;
 }
 
-sds sdscatlen(sds s, void *t, size_t len) {
+sds sdscatlen(sds s, const void *t, size_t len) {
     struct sdshdr *sh;
     size_t curlen = sdslen(s);
 
@@ -193,15 +193,15 @@ sds sdscatlen(sds s, void *t, size_t len) {
     return s;
 }
 
-sds sdscat(sds s, char *t) {
+sds sdscat(sds s, const char *t) {
     return sdscatlen(s, t, strlen(t));
 }
 
-sds sdscatsds(sds s, sds t) {
+sds sdscatsds(sds s, const sds t) {
     return sdscatlen(s, t, sdslen(t));
 }
 
-sds sdscpylen(sds s, char *t, size_t len) {
+sds sdscpylen(sds s, const char *t, size_t len) {
     struct sdshdr *sh = (void*) (s-(sizeof(struct sdshdr)));
     size_t totlen = sh->free+sh->len;
 
@@ -218,7 +218,7 @@ sds sdscpylen(sds s, char *t, size_t len) {
     return s;
 }
 
-sds sdscpy(sds s, char *t) {
+sds sdscpy(sds s, const char *t) {
     return sdscpylen(s, t, strlen(t));
 }
 
@@ -314,7 +314,7 @@ void sdstoupper(sds s) {
     for (j = 0; j < len; j++) s[j] = toupper(s[j]);
 }
 
-int sdscmp(sds s1, sds s2) {
+int sdscmp(const sds s1, const sds s2) {
     size_t l1, l2, minlen;
     int cmp;
 
@@ -342,7 +342,7 @@ int sdscmp(sds s1, sds s2) {
  * requires length arguments. sdssplit() is just the
  * same function but for zero-terminated strings.
  */
-sds *sdssplitlen(char *s, int len, char *sep, int seplen, int *count) {
+sds *sdssplitlen(const char *s, int len, const char *sep, int seplen, int *count) {
     int elements = 0, slots = 5, start = 0, j;
     sds *tokens;
 
@@ -413,7 +413,7 @@ sds sdsfromlonglong(long long value) {
     return sdsnewlen(p,32-(p-buf));
 }
 
-sds sdscatrepr(sds s, char *p, size_t len) {
+sds sdscatrepr(sds s, const char *p, size_t len) {
     s = sdscatlen(s,"\"",1);
     while(len--) {
         switch(*p) {
@@ -481,8 +481,8 @@ int hex_digit_to_int(char c) {
  * Note that sdscatrepr() is able to convert back a string into
  * a quoted string in the same format sdssplitargs() is able to parse.
  */
-sds *sdssplitargs(char *line, int *argc) {
-    char *p = line;
+sds *sdssplitargs(const char *line, int *argc) {
+    const char *p = line;
     char *current = NULL;
     char **vector = NULL;
 
@@ -604,7 +604,7 @@ void sdssplitargs_free(sds *argv, int argc) {
  *
  * The function returns the sds string pointer, that is always the same
  * as the input pointer since no resize is needed. */
-sds sdsmapchars(sds s, char *from, char *to, size_t setlen) {
+sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen) {
     size_t j, i, l = sdslen(s);
 
     for (j = 0; j < l; j++) {
diff --git a/src/sds.h b/src/sds.h
index 0648381bb..e8d306503 100644
--- a/src/sds.h
+++ b/src/sds.h
@@ -60,13 +60,13 @@ sds sdsempty();
 size_t sdslen(const sds s);
 sds sdsdup(const sds s);
 void sdsfree(sds s);
-size_t sdsavail(sds s);
+size_t sdsavail(const sds s);
 sds sdsgrowzero(sds s, size_t len);
-sds sdscatlen(sds s, void *t, size_t len);
-sds sdscat(sds s, char *t);
-sds sdscatsds(sds s, sds t);
-sds sdscpylen(sds s, char *t, size_t len);
-sds sdscpy(sds s, char *t);
+sds sdscatlen(sds s, const void *t, size_t len);
+sds sdscat(sds s, const char *t);
+sds sdscatsds(sds s, const sds t);
+sds sdscpylen(sds s, const char *t, size_t len);
+sds sdscpy(sds s, const char *t);
 
 sds sdscatvprintf(sds s, const char *fmt, va_list ap);
 #ifdef __GNUC__
@@ -80,16 +80,16 @@ sds sdstrim(sds s, const char *cset);
 sds sdsrange(sds s, int start, int end);
 void sdsupdatelen(sds s);
 void sdsclear(sds s);
-int sdscmp(sds s1, sds s2);
-sds *sdssplitlen(char *s, int len, char *sep, int seplen, int *count);
+int sdscmp(const sds s1, const sds s2);
+sds *sdssplitlen(const char *s, int len, const char *sep, int seplen, int *count);
 void sdsfreesplitres(sds *tokens, int count);
 void sdstolower(sds s);
 void sdstoupper(sds s);
 sds sdsfromlonglong(long long value);
-sds sdscatrepr(sds s, char *p, size_t len);
-sds *sdssplitargs(char *line, int *argc);
+sds sdscatrepr(sds s, const char *p, size_t len);
+sds *sdssplitargs(const char *line, int *argc);
 void sdssplitargs_free(sds *argv, int argc);
-sds sdsmapchars(sds s, char *from, char *to, size_t setlen);
+sds sdsmapchars(sds s, const char *from, const char *to, size_t setlen);
 
 /* Low level functions exposed to the user API */
 sds sdsMakeRoomFor(sds s, size_t addlen);