diff --git a/cutils.c b/cutils.c
index 012eb11..4a9ce0f 100644
--- a/cutils.c
+++ b/cutils.c
@@ -289,13 +289,13 @@ int fcntl_setfl(int fd, int flag)
  * End pointer will be returned in *end, if end is valid.
  * Return -1 on error.
  */
-ssize_t strtosz(const char *nptr, char **end)
+ssize_t strtosz(const char *nptr, char **end, int default_shift)
 {
     ssize_t retval = -1;
-    int64_t tmpval;
+    int64_t tmpval, mul;
     char *endptr;
     int mul_required = 0;
-    double val, mul = 1;
+    double val;
 
     endptr = (char *)nptr + strspn(nptr, " 0123456789");
     if (*endptr == '.') {
@@ -308,15 +308,14 @@ ssize_t strtosz(const char *nptr, char **end)
         goto fail;
 
     switch (*endptr++) {
+    case 0:
+    case ' ':
+        mul = (1ULL << default_shift);
+        break;
     case 'K':
     case 'k':
         mul = 1 << 10;
         break;
-    case 0:
-    case ' ':
-        if (mul_required) {
-            goto fail;
-        }
     case 'M':
     case 'm':
         mul = 1ULL << 20;
@@ -333,6 +332,9 @@ ssize_t strtosz(const char *nptr, char **end)
         goto fail;
     }
 
+    if (mul == 1 && mul_required) {
+        goto fail;
+    }
     tmpval = (val * mul);
     if (tmpval > ~(size_t)0)
         goto fail;
diff --git a/monitor.c b/monitor.c
index 6678fb5..0d04b27 100644
--- a/monitor.c
+++ b/monitor.c
@@ -3713,7 +3713,7 @@ static const mon_cmd_t *monitor_parse_command(Monitor *mon,
                         break;
                     }
                 }
-                val = strtosz(p, &end);
+                val = strtosz(p, &end, 0);
                 if (val < 0) {
                     monitor_printf(mon, "invalid size\n");
                     goto fail;
diff --git a/qemu-common.h b/qemu-common.h
index 0a062d4..cabd8f8 100644
--- a/qemu-common.h
+++ b/qemu-common.h
@@ -153,7 +153,7 @@ time_t mktimegm(struct tm *tm);
 int qemu_fls(int i);
 int qemu_fdatasync(int fd);
 int fcntl_setfl(int fd, int flag);
-ssize_t strtosz(const char *nptr, char **end);
+ssize_t strtosz(const char *nptr, char **end, int default_shift);
 
 /* path.c */
 void init_paths(const char *prefix);
diff --git a/vl.c b/vl.c
index 6043fa2..ae4d6f3 100644
--- a/vl.c
+++ b/vl.c
@@ -735,7 +735,7 @@ static void numa_add(const char *optarg)
             node_mem[nodenr] = 0;
         } else {
             ssize_t sval;
-            sval = strtosz(option, NULL);
+            sval = strtosz(option, NULL, 20);
             if (sval < 0) {
                 fprintf(stderr, "qemu: invalid numa mem size: %s\n", optarg);
                 exit(1);
@@ -2162,7 +2162,7 @@ int main(int argc, char **argv, char **envp)
             case QEMU_OPTION_m: {
                 ssize_t value;
 
-                value = strtosz(optarg, NULL);
+                value = strtosz(optarg, NULL, 20);
                 if (value < 0) {
                     fprintf(stderr, "qemu: invalid ram size: %s\n", optarg);
                     exit(1);