diff --git a/README.md b/README.md
index 0647db44..20244bde 100644
--- a/README.md
+++ b/README.md
@@ -31,15 +31,9 @@ functionality hasn't been implemented.  It's appropriate for early
 adopters and interested developers, not for production use.
 
 In that vein, expect significant incompatible changes to both the format
-of network messages and persistent structures.  To avoid mistakes the
-implementation currently calculates a hash of the format and ioctl
-header files in the source tree.  The kernel module will refuse to mount
-a volume created by userspace utilities with a mismatched hash, and it
-will refuse to connect to a remote node with a mismatched hash.  This
-means having to unmount, mkfs, and remount everything across many
-functional changes.  Once the format is nailed down we'll wire up
-forward and back compat machinery and remove this temporary safety
-measure. 
+of network messages and persistent structures. Since the format hash-checking
+has now been removed in preparation for release, if there is any doubt, mkfs
+is strongly recommended.
 
 The current kernel module is developed against the RHEL/CentOS 7.x
 kernel to minimize the friction of developing and testing with partners'
diff --git a/kmod/Makefile b/kmod/Makefile
index ab69272c..58963acf 100644
--- a/kmod/Makefile
+++ b/kmod/Makefile
@@ -16,11 +16,7 @@ SCOUTFS_GIT_DESCRIBE := \
 	$(shell git describe --all --abbrev=6 --long 2>/dev/null || \
 		echo no-git)
 
-SCOUTFS_FORMAT_HASH := \
-	$(shell cat src/format.h src/ioctl.h | md5sum | cut -b1-16)
-
 SCOUTFS_ARGS := SCOUTFS_GIT_DESCRIBE=$(SCOUTFS_GIT_DESCRIBE) \
-		SCOUTFS_FORMAT_HASH=$(SCOUTFS_FORMAT_HASH) \
 		CONFIG_SCOUTFS_FS=m -C $(SK_KSRC) M=$(CURDIR)/src \
 		EXTRA_CFLAGS="-Werror"
 
diff --git a/kmod/src/Makefile b/kmod/src/Makefile
index bd50ec38..db5f5576 100644
--- a/kmod/src/Makefile
+++ b/kmod/src/Makefile
@@ -1,7 +1,6 @@
 obj-$(CONFIG_SCOUTFS_FS) := scoutfs.o
 
-CFLAGS_super.o = -DSCOUTFS_GIT_DESCRIBE=\"$(SCOUTFS_GIT_DESCRIBE)\" \
-		 -DSCOUTFS_FORMAT_HASH=0x$(SCOUTFS_FORMAT_HASH)LLU
+CFLAGS_super.o = -DSCOUTFS_GIT_DESCRIBE=\"$(SCOUTFS_GIT_DESCRIBE)\"
 
 CFLAGS_scoutfs_trace.o = -I$(src) # define_trace.h double include
 
diff --git a/kmod/src/client.c b/kmod/src/client.c
index 305794ca..ffe06de8 100644
--- a/kmod/src/client.c
+++ b/kmod/src/client.c
@@ -282,10 +282,10 @@ static int client_greeting(struct super_block *sb,
 		goto out;
 	}
 
-	if (gr->format_hash != super->format_hash) {
+	if (gr->version != super->version) {
 		scoutfs_warn(sb, "server sent format 0x%llx, client has 0x%llx",
-			     le64_to_cpu(gr->format_hash),
-			     le64_to_cpu(super->format_hash));
+			     le64_to_cpu(gr->version),
+			     le64_to_cpu(super->version));
 		ret = -EINVAL;
 		goto out;
 	}
@@ -394,7 +394,7 @@ static void scoutfs_client_connect_worker(struct work_struct *work)
 
 	/* send a greeting to verify endpoints of each connection */
 	greet.fsid = super->hdr.fsid;
-	greet.format_hash = super->format_hash;
+	greet.version = super->version;
 	greet.server_term = cpu_to_le64(client->server_term);
 	greet.unmount_barrier = cpu_to_le64(client->greeting_umb);
 	greet.rid = cpu_to_le64(sbi->rid);
diff --git a/kmod/src/format.h b/kmod/src/format.h
index 033552bf..93582637 100644
--- a/kmod/src/format.h
+++ b/kmod/src/format.h
@@ -1,6 +1,9 @@
 #ifndef _SCOUTFS_FORMAT_H_
 #define _SCOUTFS_FORMAT_H_
 
+#define SCOUTFS_INTEROP_VERSION		0ULL
+#define SCOUTFS_INTEROP_VERSION_STR	__stringify(0)
+
 /* statfs(2) f_type */
 #define SCOUTFS_SUPER_MAGIC	0x554f4353		/* "SCOU" */
 
@@ -596,7 +599,7 @@ struct scoutfs_quorum_block {
 struct scoutfs_super_block {
 	struct scoutfs_block_header hdr;
 	__le64 id;
-	__le64 format_hash;
+	__le64 version;
 	__le64 flags;
 	__u8 uuid[SCOUTFS_UUID_BYTES];
 	__le64 next_ino;
@@ -759,7 +762,7 @@ enum scoutfs_dentry_type {
  */
 struct scoutfs_net_greeting {
 	__le64 fsid;
-	__le64 format_hash;
+	__le64 version;
 	__le64 server_term;
 	__le64 unmount_barrier;
 	__le64 rid;
diff --git a/kmod/src/server.c b/kmod/src/server.c
index 57a7e8d5..958343a1 100644
--- a/kmod/src/server.c
+++ b/kmod/src/server.c
@@ -1141,10 +1141,10 @@ static int server_greeting(struct super_block *sb,
 		goto send_err;
 	}
 
-	if (gr->format_hash != super->format_hash) {
+	if (gr->version != super->version) {
 		scoutfs_warn(sb, "client sent format 0x%llx, server has 0x%llx",
-			     le64_to_cpu(gr->format_hash),
-			     le64_to_cpu(super->format_hash));
+			     le64_to_cpu(gr->version),
+			     le64_to_cpu(super->version));
 		ret = -EINVAL;
 		goto send_err;
 	}
@@ -1173,7 +1173,7 @@ send_err:
 	err = ret;
 
 	greet.fsid = super->hdr.fsid;
-	greet.format_hash = super->format_hash;
+	greet.version = super->version;
 	greet.server_term = cpu_to_le64(server->term);
 	greet.unmount_barrier = umb;
 	greet.rid = gr->rid;
diff --git a/kmod/src/super.c b/kmod/src/super.c
index 926531d6..a04150e1 100644
--- a/kmod/src/super.c
+++ b/kmod/src/super.c
@@ -352,10 +352,10 @@ static int scoutfs_read_super_from_bdev(struct super_block *sb,
 	}
 
 
-	if (super->format_hash != cpu_to_le64(SCOUTFS_FORMAT_HASH)) {
-		scoutfs_err(sb, "super block has invalid format hash 0x%llx, expected 0x%llx",
-			    le64_to_cpu(super->format_hash),
-			    SCOUTFS_FORMAT_HASH);
+	if (super->version != cpu_to_le64(SCOUTFS_INTEROP_VERSION)) {
+		scoutfs_err(sb, "super block has invalid version %llu, expected %llu",
+			    le64_to_cpu(super->version),
+			    SCOUTFS_INTEROP_VERSION);
 		ret = -EINVAL;
 		goto out;
 	}
@@ -682,6 +682,10 @@ static int __init scoutfs_module_init(void)
 		".section	.note.git_describe,\"a\"\n"
 		".string	\""SCOUTFS_GIT_DESCRIBE"\\n\"\n"
 		".previous\n");
+	__asm__ __volatile__ (
+		".section	.note.scoutfs_interop_version,\"a\"\n"
+		".string	\""SCOUTFS_INTEROP_VERSION_STR"\\n\"\n"
+		".previous\n");
 
 	scoutfs_init_counters();
 
@@ -714,3 +718,4 @@ module_exit(scoutfs_module_exit)
 MODULE_AUTHOR("Zach Brown <zab@versity.com>");
 MODULE_LICENSE("GPL");
 MODULE_INFO(git_describe, SCOUTFS_GIT_DESCRIBE);
+MODULE_INFO(scoutfs_interop_version, SCOUTFS_INTEROP_VERSION_STR);
diff --git a/utils/Makefile b/utils/Makefile
index 10eb66aa..e0f76142 100644
--- a/utils/Makefile
+++ b/utils/Makefile
@@ -1,23 +1,11 @@
 #
-# The userspace utils and kernel module share definitions of physical
-# structures and ioctls.  If we're in the repo we include the kmod
-# headers directly, and hash them directly to calculate the format hash.
-#
 # If we're creating a standalone tarball for distribution we copy the
 # headers out of the kmod dir into the tarball.  And then when we're
 # building in that tarball we use the headers in src/ directly.
 #
 FMTIOC_H := format.h ioctl.h
-FMTIOC_DIST := $(addprefix src/,$(FMTIOC_H))
 FMTIOC_KMOD := $(addprefix ../kmod/src/,$(FMTIOC_H))
 
-ifneq ($(wildcard $(firstword $(FMTIOC_KMOD))),)
-HASH_FILES := $(FMTIOC_KMOD)
-else
-HASH_FILES := $(FMTIOC_DIST)
-endif
-SCOUTFS_FORMAT_HASH := $(shell cat $(HASH_FILES) | md5sum | cut -b1-16)
-
 CFLAGS := -Wall -O2 -Werror -D_FILE_OFFSET_BITS=64 -g -msse4.2 \
 	-fno-strict-aliasing \
 	-DSCOUTFS_FORMAT_HASH=0x$(SCOUTFS_FORMAT_HASH)LLU
diff --git a/utils/src/mkfs.c b/utils/src/mkfs.c
index 7d3b582b..f5306dd1 100644
--- a/utils/src/mkfs.c
+++ b/utils/src/mkfs.c
@@ -205,7 +205,7 @@ static int do_mkfs(struct mkfs_args *args)
 	pseudo_random_bytes(&super->hdr.fsid, sizeof(super->hdr.fsid));
 	super->hdr.magic = cpu_to_le32(SCOUTFS_BLOCK_MAGIC_SUPER);
 	super->hdr.seq = cpu_to_le64(1);
-	super->format_hash = cpu_to_le64(SCOUTFS_FORMAT_HASH);
+	super->version = cpu_to_le64(SCOUTFS_INTEROP_VERSION);
 	uuid_generate(super->uuid);
 	super->next_ino = cpu_to_le64(SCOUTFS_ROOT_INO + 1);
 	super->next_trans_seq = cpu_to_le64(1);
@@ -352,7 +352,7 @@ static int do_mkfs(struct mkfs_args *args)
 	       "  meta device path:     %s\n"
 	       "  data device path:     %s\n"
 	       "  fsid:                 %llx\n"
-	       "  format hash:          %llx\n"
+	       "  version:              %llx\n"
 	       "  uuid:                 %s\n"
 	       "  64KB metadata blocks: "SIZE_FMT"\n"
 	       "  4KB data blocks:      "SIZE_FMT"\n"
@@ -360,7 +360,7 @@ static int do_mkfs(struct mkfs_args *args)
 		args->meta_device,
 	        args->data_device,
 		le64_to_cpu(super->hdr.fsid),
-		le64_to_cpu(super->format_hash),
+		le64_to_cpu(super->version),
 		uuid_str,
 		SIZE_ARGS(le64_to_cpu(super->total_meta_blocks),
 			  SCOUTFS_BLOCK_LG_SIZE),
diff --git a/utils/src/print.c b/utils/src/print.c
index 968068a5..c2ba30a2 100644
--- a/utils/src/print.c
+++ b/utils/src/print.c
@@ -860,8 +860,8 @@ static void print_super_block(struct scoutfs_super_block *super, u64 blkno)
 
 	printf("super blkno %llu\n", blkno);
 	print_block_header(&super->hdr, SCOUTFS_BLOCK_SM_SIZE);
-	printf("  format_hash %llx uuid %s\n",
-	       le64_to_cpu(super->format_hash), uuid_str);
+	printf("  version %llx uuid %s\n",
+	       le64_to_cpu(super->version), uuid_str);
 	printf("  flags: 0x%016llx\n", le64_to_cpu(super->flags));
 
 	server_addr = alloc_addr_str(&super->server_addr);