diff --git a/hw/i386/x86.c b/hw/i386/x86.c
index d8bb5c2a96..9b9a4d5837 100644
--- a/hw/i386/x86.c
+++ b/hw/i386/x86.c
@@ -612,6 +612,7 @@ void x86_load_linux(X86MachineState *x86ms,
     vmode = strstr(kernel_cmdline, "vga=");
     if (vmode) {
         unsigned int video_mode;
+        const char *end;
         int ret;
         /* skip "vga=" */
         vmode += 4;
@@ -622,10 +623,9 @@ void x86_load_linux(X86MachineState *x86ms,
         } else if (!strncmp(vmode, "ask", 3)) {
             video_mode = 0xfffd;
         } else {
-            ret = qemu_strtoui(vmode, NULL, 0, &video_mode);
-            if (ret != 0) {
-                fprintf(stderr, "qemu: can't parse 'vga' parameter: %s\n",
-                        strerror(-ret));
+            ret = qemu_strtoui(vmode, &end, 0, &video_mode);
+            if (ret != 0 || (*end && *end != ' ')) {
+                fprintf(stderr, "qemu: invalid 'vga=' kernel parameter.\n");
                 exit(1);
             }
         }