diff --git a/lfs3.c b/lfs3.c
index ed33942a..a3e3b9f4 100644
--- a/lfs3.c
+++ b/lfs3.c
@@ -16540,9 +16540,9 @@ failed:;
 // enable the global on-disk block-map
 #if !defined(LFS3_RDONLY) && defined(LFS3_GBMAP) && !defined(LFS3_YES_GBMAP)
 int lfs3_fs_mkgbmap(lfs3_t *lfs3) {
-    // do nothing if we already have a gbmap
+    // error if we already have a gbmap
     if (lfs3_f_isgbmap(lfs3->flags)) {
-        return 0;
+        return LFS3_ERR_EXIST;
     }
 
     // prepare our filesystem for writing
@@ -16599,9 +16599,9 @@ failed:;
 // disable the global on-disk block-map
 #if !defined(LFS3_RDONLY) && defined(LFS3_GBMAP) && !defined(LFS3_YES_GBMAP)
 int lfs3_fs_rmgbmap(lfs3_t *lfs3) {
-    // do nothing if we already don't have a gbmap
+    // error if we already don't have a gbmap
     if (!lfs3_f_isgbmap(lfs3->flags)) {
-        return 0;
+        return LFS3_ERR_NOENT;
     }
 
     // prepare our filesystem for writing
diff --git a/tests/test_gbmap.toml b/tests/test_gbmap.toml
index f869937c..a13c64b7 100644
--- a/tests/test_gbmap.toml
+++ b/tests/test_gbmap.toml
@@ -1167,3 +1167,297 @@ code = '''
 
     lfs3_unmount(&lfs3) => 0;
 '''
+
+# test that removing a non-existant gbmap errors
+[cases.test_gbmap_rmgbmap_noent]
+ifndef = 'LFS3_YES_GBMAP'
+defines.COUNT = [
+    'BLOCK_COUNT',
+    'BLOCK_COUNT-1',
+    'BLOCK_COUNT/2',
+    'BLOCK_COUNT/4',
+    '5',
+    '3',
+]
+defines.SIZE = [
+    'BLOCK_SIZE',
+    '2*BLOCK_SIZE',
+    '8*BLOCK_SIZE',
+]
+defines.N = ['5', 'BLOCK_COUNT/2']
+defines.WRAPAROUND = 3
+# REMOUNT=0 => don't remount
+# REMOUNT=1 => remount after
+# REMOUNT=2 => remount before
+# REMOUNT=3 => remount both after and before
+defines.REMOUNT = [0, 1, 2, 3]
+if = [
+    'COUNT >= 3',
+    'COUNT >= 2*N*SIZE/BLOCK_SIZE',
+]
+code = '''
+    // test various block counts
+    struct lfs3_cfg cfg = *CFG;
+    cfg.block_count = COUNT;
+    lfs3_t lfs3;
+    // note the lack of gbmap flag
+    lfs3_format(&lfs3, LFS3_F_RDWR, &cfg) => 0;
+    lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+
+    // check that we were formatted without the gbmap
+    struct lfs3_fsinfo fsinfo;
+    lfs3_fs_stat(&lfs3, &fsinfo) => 0;
+    assert(!(fsinfo.flags & LFS3_I_GBMAP));
+
+    // create n files repeatedly until we're sure we've wrapped around
+    // a few times
+    uint32_t prng = 42;
+    uint32_t prng_ = prng;
+    for (lfs3_size_t i = 0;
+            i < (WRAPAROUND*COUNT)
+                / (N*(SIZE/BLOCK_SIZE));
+            i++) {
+        prng = prng_;
+        for (lfs3_size_t n = 0; n < N; n++) {
+            char name[256];
+            sprintf(name, "file%08d", n);
+
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            lfs3_file_open(&lfs3, &file, name,
+                    LFS3_O_WRONLY | LFS3_O_CREAT | LFS3_O_TRUNC) => 0;
+            lfs3_file_write(&lfs3, &file, wbuf, SIZE) => SIZE;
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    // remount before?
+    if (REMOUNT & 2) {
+        lfs3_unmount(&lfs3) => 0;
+        lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+    }
+
+    // now try to remove the gbmap
+    lfs3_fs_rmgbmap(&lfs3) => LFS3_ERR_NOENT;
+
+    // remount after?
+    if (REMOUNT & 1) {
+        lfs3_unmount(&lfs3) => 0;
+        lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+    }
+
+    // we should no longer have a gbmap
+    lfs3_fs_stat(&lfs3, &fsinfo) => 0;
+    assert(!(fsinfo.flags & LFS3_I_GBMAP));
+
+    // create n files repeatedly until we're sure we've wrapped around
+    // a few times
+    for (lfs3_size_t i = 0;
+            i < (WRAPAROUND*COUNT)
+                / (N*(SIZE/BLOCK_SIZE));
+            i++) {
+        prng = prng_;
+        for (lfs3_size_t n = 0; n < N; n++) {
+            char name[256];
+            sprintf(name, "file%08d", n);
+
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            lfs3_file_open(&lfs3, &file, name,
+                    LFS3_O_WRONLY | LFS3_O_CREAT | LFS3_O_TRUNC) => 0;
+            lfs3_file_write(&lfs3, &file, wbuf, SIZE) => SIZE;
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    for (int remount = 0; remount < 2; remount++) {
+        // remount?
+        if (remount) {
+            lfs3_unmount(&lfs3) => 0;
+            lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+        }
+
+        // check that our file writes worked
+        prng_ = prng;
+        for (lfs3_size_t i = 0; i < N; i++) {
+            // check with stat
+            char name[256];
+            sprintf(name, "file%08d", i);
+            struct lfs3_info info;
+            lfs3_stat(&lfs3, name, &info) => 0;
+            assert(strcmp(info.name, name) == 0);
+            assert(info.type == LFS3_TYPE_REG);
+            assert(info.size == SIZE);
+
+            // try reading the file, note we reset prng above
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            uint8_t rbuf[SIZE];
+            lfs3_file_open(&lfs3, &file, name, LFS3_O_RDONLY) => 0;
+            lfs3_file_read(&lfs3, &file, rbuf, SIZE) => SIZE;
+            assert(memcmp(rbuf, wbuf, SIZE) == 0);
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    lfs3_unmount(&lfs3) => 0;
+'''
+
+# test that making an existant gbmap errors
+[cases.test_gbmap_mkgbmap_exist]
+ifndef = 'LFS3_YES_GBMAP'
+defines.COUNT = [
+    'BLOCK_COUNT',
+    'BLOCK_COUNT-1',
+    'BLOCK_COUNT/2',
+    'BLOCK_COUNT/4',
+    '5',
+    '3',
+]
+defines.SIZE = [
+    'BLOCK_SIZE',
+    '2*BLOCK_SIZE',
+    '8*BLOCK_SIZE',
+]
+defines.N = ['5', 'BLOCK_COUNT/2']
+defines.WRAPAROUND = 3
+# REMOUNT=0 => don't remount
+# REMOUNT=1 => remount after
+# REMOUNT=2 => remount before
+# REMOUNT=3 => remount both after and before
+defines.REMOUNT = [0, 1, 2, 3]
+if = [
+    'COUNT >= 3',
+    'COUNT >= 2*N*SIZE/BLOCK_SIZE',
+]
+code = '''
+    // test various block counts
+    struct lfs3_cfg cfg = *CFG;
+    cfg.block_count = COUNT;
+    lfs3_t lfs3;
+    // note the gbmap flag
+    lfs3_format(&lfs3, LFS3_F_RDWR | LFS3_F_GBMAP, &cfg) => 0;
+    lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+
+    // check that we were formatted with the gbmap
+    struct lfs3_fsinfo fsinfo;
+    lfs3_fs_stat(&lfs3, &fsinfo) => 0;
+    assert(fsinfo.flags & LFS3_I_GBMAP);
+
+    // create n files repeatedly until we're sure we've wrapped around
+    // a few times
+    uint32_t prng = 42;
+    uint32_t prng_ = prng;
+    for (lfs3_size_t i = 0;
+            i < (WRAPAROUND*COUNT)
+                / (N*(SIZE/BLOCK_SIZE));
+            i++) {
+        prng = prng_;
+        for (lfs3_size_t n = 0; n < N; n++) {
+            char name[256];
+            sprintf(name, "file%08d", n);
+
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            lfs3_file_open(&lfs3, &file, name,
+                    LFS3_O_WRONLY | LFS3_O_CREAT | LFS3_O_TRUNC) => 0;
+            lfs3_file_write(&lfs3, &file, wbuf, SIZE) => SIZE;
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    // remount before?
+    if (REMOUNT & 2) {
+        lfs3_unmount(&lfs3) => 0;
+        lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+    }
+
+    // now make the gbmap
+    lfs3_fs_mkgbmap(&lfs3) => LFS3_ERR_EXIST;
+
+    // remount after?
+    if (REMOUNT & 1) {
+        lfs3_unmount(&lfs3) => 0;
+        lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+    }
+
+    // we should now have a gbmap
+    lfs3_fs_stat(&lfs3, &fsinfo) => 0;
+    assert(fsinfo.flags & LFS3_I_GBMAP);
+
+    // create n files repeatedly until we're sure we've wrapped around
+    // a few times
+    for (lfs3_size_t i = 0;
+            i < (WRAPAROUND*COUNT)
+                / (N*(SIZE/BLOCK_SIZE));
+            i++) {
+        prng = prng_;
+        for (lfs3_size_t n = 0; n < N; n++) {
+            char name[256];
+            sprintf(name, "file%08d", n);
+
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            lfs3_file_open(&lfs3, &file, name,
+                    LFS3_O_WRONLY | LFS3_O_CREAT | LFS3_O_TRUNC) => 0;
+            lfs3_file_write(&lfs3, &file, wbuf, SIZE) => SIZE;
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    for (int remount = 0; remount < 2; remount++) {
+        // remount?
+        if (remount) {
+            lfs3_unmount(&lfs3) => 0;
+            lfs3_mount(&lfs3, LFS3_M_RDWR, &cfg) => 0;
+        }
+
+        // check that our file writes worked
+        prng_ = prng;
+        for (lfs3_size_t i = 0; i < N; i++) {
+            // check with stat
+            char name[256];
+            sprintf(name, "file%08d", i);
+            struct lfs3_info info;
+            lfs3_stat(&lfs3, name, &info) => 0;
+            assert(strcmp(info.name, name) == 0);
+            assert(info.type == LFS3_TYPE_REG);
+            assert(info.size == SIZE);
+
+            // try reading the file, note we reset prng above
+            uint8_t wbuf[SIZE];
+            for (lfs3_size_t j = 0; j < SIZE; j++) {
+                wbuf[j] = 'a' + (TEST_PRNG(&prng_) % 26);
+            }
+
+            lfs3_file_t file;
+            uint8_t rbuf[SIZE];
+            lfs3_file_open(&lfs3, &file, name, LFS3_O_RDONLY) => 0;
+            lfs3_file_read(&lfs3, &file, rbuf, SIZE) => SIZE;
+            assert(memcmp(rbuf, wbuf, SIZE) == 0);
+            lfs3_file_close(&lfs3, &file) => 0;
+        }
+    }
+
+    lfs3_unmount(&lfs3) => 0;
+'''