diff --git a/lib/internal.h b/lib/internal.h
index fb265eef..5d776003 100644
--- a/lib/internal.h
+++ b/lib/internal.h
@@ -75,6 +75,8 @@ int device_block_size(struct device *device);
 int device_read_ahead(struct device *device, uint32_t *read_ahead);
 int device_size(struct device *device, uint64_t *size);
 int device_open(struct device *device, int flags);
+void device_disable_direct_io(struct device *device);
+
 
 enum devcheck { DEV_OK = 0, DEV_EXCL = 1, DEV_SHARED = 2 };
 int device_block_adjust(struct crypt_device *cd,
diff --git a/lib/luks1/keymanage.c b/lib/luks1/keymanage.c
index 44673c39..16968fbc 100644
--- a/lib/luks1/keymanage.c
+++ b/lib/luks1/keymanage.c
@@ -545,6 +545,16 @@ int LUKS_read_phdr(struct luks_phdr *hdr,
 	if (!r)
 		r = LUKS_check_device_size(ctx, hdr->keyBytes);
 
+	/*
+	 * Cryptsetup 1.0.0 did not align keyslots to 4k (very rare version).
+	 * Disable direct-io to avoid possible IO errors if underlying device
+	 * has bigger sector size.
+	 */
+	if (!r && hdr->keyblock[0].keyMaterialOffset * SECTOR_SIZE < LUKS_ALIGN_KEYSLOTS) {
+		log_dbg("Old unaligned LUKS keyslot detected, disabling direct-io.");
+		device_disable_direct_io(device);
+	}
+
 	close(devfd);
 	return r;
 }
diff --git a/lib/utils_device.c b/lib/utils_device.c
index 72899338..8c4d4349 100644
--- a/lib/utils_device.c
+++ b/lib/utils_device.c
@@ -530,3 +530,8 @@ size_t size_round_up(size_t size, unsigned int block)
 	size_t s = (size + (block - 1)) / block;
 	return s * block;
 }
+
+void device_disable_direct_io(struct device *device)
+{
+	device->o_direct = 0;
+}