diff --git a/sys/riscv/include/memdev.h b/sys/riscv/include/memdev.h
index cbd8a2a3c6e0..8fe431bc1fe3 100644
--- a/sys/riscv/include/memdev.h
+++ b/sys/riscv/include/memdev.h
@@ -35,6 +35,6 @@
 d_open_t	memopen;
 d_read_t	memrw;
 d_ioctl_t	memioctl_md;
-#define		memmmap		(d_mmap_t *)NULL
+d_mmap_t	memmmap;
 
 #endif /* _MACHINE_MEMDEV_H_ */
diff --git a/sys/riscv/riscv/mem.c b/sys/riscv/riscv/mem.c
index ccd981cc6533..ec0a29bdf5cd 100644
--- a/sys/riscv/riscv/mem.c
+++ b/sys/riscv/riscv/mem.c
@@ -122,6 +122,21 @@ memrw(struct cdev *dev, struct uio *uio, int flags)
 	return (error);
 }
 
+/*
+ * Allow user processes to MMAP some memory sections
+ * instead of going through read/write.
+ */
+int
+memmmap(struct cdev *dev, vm_ooffset_t offset, vm_paddr_t *paddr,
+    int prot __unused, vm_memattr_t *memattr __unused)
+{
+	if (dev2unit(dev) == CDEV_MINOR_MEM) {
+		*paddr = offset;
+		return (0);
+	}
+	return (-1);
+}
+
 int
 memioctl_md(struct cdev *dev __unused, u_long cmd __unused,
     caddr_t data __unused, int flags __unused, struct thread *td __unused)