--- b/sys/netsmb/smb_smb.c	
+++ b/sys/netsmb/smb_smb.c	
@@ -771,7 +771,12 @@ 
 	u_int8_t wc;
 	int error, rlen, blksz;
 
-	if (SSTOVC(ssp)->vc_sopt.sv_caps & SMB_CAP_LARGE_READX)
+	if (uio->uio_offset > UINT32_MAX
+		&& !(SSTOVC(ssp)->vc_sopt.sv_caps & SMB_CAP_LARGE_FILES)) {
+		return (EFBIG);
+	}
+
+	if (SSTOVC(ssp)->vc_sopt.sv_caps & (SMB_CAP_LARGE_READX | SMB_CAP_LARGE_FILES))
 		return (smb_smb_readx(ssp, fid, len, rresid, uio, scred));
 
 	error = smb_rq_alloc(SSTOCP(ssp), SMB_COM_READ, scred, &rqp);
@@ -850,7 +855,12 @@ 
 	u_int8_t wc;
 	int error, blksz;
 
-	if (*len && SSTOVC(ssp)->vc_sopt.sv_caps & SMB_CAP_LARGE_WRITEX)
+	if (uio->uio_offset > UINT32_MAX
+		&& !(SSTOVC(ssp)->vc_sopt.sv_caps & SMB_CAP_LARGE_FILES)) {
+		return (EFBIG);
+	}
+
+	if (*len && SSTOVC(ssp)->vc_sopt.sv_caps & (SMB_CAP_LARGE_WRITEX | SMB_CAP_LARGE_FILES))
 		return (smb_smb_writex(ssp, fid, len, rresid, uio, scred));
  
 	blksz = SSTOVC(ssp)->vc_txmax - SMB_HDRLEN - 16;