diff --git a/src/sds.c b/src/sds.c
index 5a3bc82b..11f560ad 100644
--- a/src/sds.c
+++ b/src/sds.c
@@ -570,7 +570,7 @@ sds sdstrim(sds s, const char *cset) {
     sp = start = s;
     ep = end = s+sdslen(s)-1;
     while(sp <= end && strchr(cset, *sp)) sp++;
-    while(ep > start && strchr(cset, *ep)) ep--;
+    while(ep > sp && strchr(cset, *ep)) ep--;
     len = (sp > ep) ? 0 : ((ep-sp)+1);
     if (sh->buf != sp) memmove(sh->buf, sp, len);
     sh->buf[len] = '\0';