diff --git a/tools/include/xen-sys/Linux/privcmd.h b/tools/include/xen-sys/Linux/privcmd.h
index 9531b728f9..bc60e8fd55 100644
--- a/tools/include/xen-sys/Linux/privcmd.h
+++ b/tools/include/xen-sys/Linux/privcmd.h
@@ -114,5 +114,7 @@ typedef struct privcmd_mmap_resource {
 	_IOC(_IOC_NONE, 'P', 6, sizeof(domid_t))
 #define IOCTL_PRIVCMD_MMAP_RESOURCE				\
 	_IOC(_IOC_NONE, 'P', 7, sizeof(privcmd_mmap_resource_t))
+#define IOCTL_PRIVCMD_UNIMPLEMENTED				\
+	_IOC(_IOC_NONE, 'P', 0xFF, 0)
 
 #endif /* __LINUX_PUBLIC_PRIVCMD_H__ */
diff --git a/tools/libs/foreignmemory/linux.c b/tools/libs/foreignmemory/linux.c
index 3686cf41e0..0368aa09f4 100644
--- a/tools/libs/foreignmemory/linux.c
+++ b/tools/libs/foreignmemory/linux.c
@@ -53,6 +53,23 @@ int osdep_xenforeignmemory_open(xenforeignmemory_handle *fmem)
         return -1;
     }
 
+    /*
+     * Older versions of privcmd return -EINVAL for unimplemented ioctls
+     * so we need to probe for the errno to use rather than just using
+     * the conventional ENOTTY.
+     */
+    if ( ioctl(fd, IOCTL_PRIVCMD_UNIMPLEMENTED, NULL) >= 0 )
+    {
+        xtl_log(fmem->logger, XTL_ERROR, -1, "xenforeignmemory",
+                "privcmd ioctl should not be implemented");
+        return -1;
+    }
+    else
+    {
+        fmem->unimpl_errno = errno;
+        errno = 0;
+    }
+
     fmem->fd = fd;
     return 0;
 }
@@ -307,7 +324,7 @@ int osdep_xenforeignmemory_map_resource(
     {
         int saved_errno;
 
-        if ( errno != ENOTTY && errno != EOPNOTSUPP )
+        if ( errno != fmem->unimpl_errno && errno != EOPNOTSUPP )
             PERROR("ioctl failed");
         else
             errno = EOPNOTSUPP;
diff --git a/tools/libs/foreignmemory/private.h b/tools/libs/foreignmemory/private.h
index b06ce12583..8f1bf081ed 100644
--- a/tools/libs/foreignmemory/private.h
+++ b/tools/libs/foreignmemory/private.h
@@ -23,6 +23,7 @@ struct xenforeignmemory_handle {
     unsigned flags;
     int fd;
     Xentoolcore__Active_Handle tc_ah;
+    int unimpl_errno;
 };
 
 int osdep_xenforeignmemory_open(xenforeignmemory_handle *fmem);