diff --git a/src/config.c b/src/config.c
index 05cb7c9f..4132c830 100644
--- a/src/config.c
+++ b/src/config.c
@@ -609,6 +609,7 @@ void loadServerConfig(char *filename, char *options) {
 void configSetCommand(redisClient *c) {
     robj *o;
     long long ll;
+    int err;
     redisAssertWithInfo(c,c->argv[2],sdsEncodedObject(c->argv[2]));
     redisAssertWithInfo(c,c->argv[3],sdsEncodedObject(c->argv[3]));
     o = c->argv[3];
@@ -628,8 +629,8 @@ void configSetCommand(redisClient *c) {
         zfree(server.masterauth);
         server.masterauth = ((char*)o->ptr)[0] ? zstrdup(o->ptr) : NULL;
     } else if (!strcasecmp(c->argv[2]->ptr,"maxmemory")) {
-        if (getLongLongFromObject(o,&ll) == REDIS_ERR ||
-            ll < 0) goto badfmt;
+        ll = memtoll(o->ptr,&err);
+        if (err || ll < 0) goto badfmt;
         server.maxmemory = ll;
         if (server.maxmemory) {
             if (server.maxmemory < zmalloc_used_memory()) {
@@ -851,7 +852,6 @@ void configSetCommand(redisClient *c) {
          * whole configuration string or accept it all, even if a single
          * error in a single client class is present. */
         for (j = 0; j < vlen; j++) {
-            char *eptr;
             long val;
 
             if ((j % 4) == 0) {
@@ -860,8 +860,8 @@ void configSetCommand(redisClient *c) {
                     goto badfmt;
                 }
             } else {
-                val = strtoll(v[j], &eptr, 10);
-                if (eptr[0] != '\0' || val < 0) {
+                val = memtoll(v[j], &err);
+                if (err || val < 0) {
                     sdsfreesplitres(v,vlen);
                     goto badfmt;
                 }
@@ -895,7 +895,8 @@ void configSetCommand(redisClient *c) {
         if (getLongLongFromObject(o,&ll) == REDIS_ERR || ll <= 0) goto badfmt;
         server.repl_timeout = ll;
     } else if (!strcasecmp(c->argv[2]->ptr,"repl-backlog-size")) {
-        if (getLongLongFromObject(o,&ll) == REDIS_ERR || ll <= 0) goto badfmt;
+        ll = memtoll(o->ptr,&err);
+        if (err || ll < 0) goto badfmt;
         resizeReplicationBacklog(ll);
     } else if (!strcasecmp(c->argv[2]->ptr,"repl-backlog-ttl")) {
         if (getLongLongFromObject(o,&ll) == REDIS_ERR || ll < 0) goto badfmt;
diff --git a/src/util.c b/src/util.c
index c5386f3a..91c4d687 100644
--- a/src/util.c
+++ b/src/util.c
@@ -38,6 +38,7 @@
 #include <sys/time.h>
 #include <float.h>
 #include <stdint.h>
+#include <errno.h>
 
 #include "util.h"
 #include "sha1.h"
@@ -170,11 +171,12 @@ int stringmatch(const char *pattern, const char *string, int nocase) {
 }
 
 /* Convert a string representing an amount of memory into the number of
- * bytes, so for instance memtoll("1Gi") will return 1073741824 that is
+ * bytes, so for instance memtoll("1Gb") will return 1073741824 that is
  * (1024*1024*1024).
  *
  * On parsing error, if *err is not NULL, it's set to 1, otherwise it's
- * set to 0 */
+ * set to 0. On error the function return value is 0, regardless of the
+ * fact 'err' is NULL or not. */
 long long memtoll(const char *p, int *err) {
     const char *u;
     char buf[128];
@@ -183,6 +185,7 @@ long long memtoll(const char *p, int *err) {
     unsigned int digits;
 
     if (err) *err = 0;
+
     /* Search the first non digit character. */
     u = p;
     if (*u == '-') u++;
@@ -203,16 +206,26 @@ long long memtoll(const char *p, int *err) {
         mul = 1024L*1024*1024;
     } else {
         if (err) *err = 1;
-        mul = 1;
+        return 0;
     }
+
+    /* Copy the digits into a buffer, we'll use strtoll() to convert
+     * the digit (without the unit) into a number. */
     digits = u-p;
     if (digits >= sizeof(buf)) {
         if (err) *err = 1;
-        return LLONG_MAX;
+        return 0;
     }
     memcpy(buf,p,digits);
     buf[digits] = '\0';
-    val = strtoll(buf,NULL,10);
+
+    char *endptr;
+    errno = 0;
+    val = strtoll(buf,&endptr,10);
+    if ((val == 0 && errno == EINVAL) || *endptr != '\0') {
+        if (err) *err = 1;
+        return 0;
+    }
     return val*mul;
 }