diff --git a/commands/simple/df.c b/commands/simple/df.c
index da83d0553..ef290c2cc 100755
--- a/commands/simple/df.c
+++ b/commands/simple/df.c
@@ -302,10 +302,10 @@ int df(const struct mtab *mt)
 	return(1);
   }
 
-  if(sp->s_magic != SUPER_V3) block_size = STATIC_BLOCK_SIZE;
+  if(sp->s_magic != SUPER_V3) block_size = _STATIC_BLOCK_SIZE;
   else block_size = super.s_block_size;
 
-  if(block_size < MIN_BLOCK_SIZE || block_size > MAX_BLOCK_SIZE) {
+  if(block_size < _MIN_BLOCK_SIZE || block_size > _MAX_BLOCK_SIZE) {
 	fprintf(stderr, "df: %s: funny block size (%d)\n",
 		mt->devname, block_size);
 	close(fd);
@@ -405,7 +405,7 @@ bit_t bit_count(unsigned blocks, bit_t bits, int fd, int block_size)
   int i, b;
   bit_t busy;
   char *wlim;
-  static char buf[MAX_BLOCK_SIZE];
+  static char buf[_MAX_BLOCK_SIZE];
   static char bits_in_char[1 << CHAR_BIT];
 
   /* Precalculate bitcount for each char. */
diff --git a/commands/simple/fsck.c b/commands/simple/fsck.c
index a1ef8edd7..413611a6a 100755
--- a/commands/simple/fsck.c
+++ b/commands/simple/fsck.c
@@ -1476,7 +1476,7 @@ char *f, **clist, **ilist, **zlist;
 
   getsuper();
 
-  if(block_size < MIN_BLOCK_SIZE || block_size > MAX_BLOCK_SIZE)
+  if(block_size < _MIN_BLOCK_SIZE || block_size > _MAX_BLOCK_SIZE)
   	fatal("funny block size");
 
   if(!(rwbuf = malloc(block_size))) fatal("couldn't allocate fs buf (1)");
diff --git a/commands/simple/fsck1.c b/commands/simple/fsck1.c
index b4ed89744..92dd6a13e 100755
--- a/commands/simple/fsck1.c
+++ b/commands/simple/fsck1.c
@@ -56,7 +56,7 @@
 #include <stdio.h>
 #include <dirent.h>
 
-#define BLOCK_SIZE STATIC_BLOCK_SIZE
+#define BLOCK_SIZE _STATIC_BLOCK_SIZE
 
 #define BITSHIFT	  4	/* = log2(#bits(int)) */
 
diff --git a/commands/simple/mkfs.c b/commands/simple/mkfs.c
index b6ad41977..9613e87d1 100755
--- a/commands/simple/mkfs.c
+++ b/commands/simple/mkfs.c
@@ -196,11 +196,11 @@ char *argv[];
 	}
 
   if(fs_version == 3) {
-  	if(!block_size) block_size = MAX_BLOCK_SIZE; /* V3 default block size */
-  	if(block_size%SECTOR_SIZE || block_size < MIN_BLOCK_SIZE) {
+  	if(!block_size) block_size = _MAX_BLOCK_SIZE; /* V3 default block size */
+  	if(block_size%SECTOR_SIZE || block_size < _MIN_BLOCK_SIZE) {
   		fprintf(stderr, "block size must be multiple of sector (%d) "
   			"and at least %d bytes\n",
-  			SECTOR_SIZE, MIN_BLOCK_SIZE);
+  			SECTOR_SIZE, _MIN_BLOCK_SIZE);
   		pexit("specified block size illegal");
   	}
   	if(block_size%V2_INODE_SIZE) {
@@ -212,7 +212,7 @@ char *argv[];
   	if(block_size) {
 	  	pexit("Can't specify a block size if FS version is <3");
   	}
- 	block_size = STATIC_BLOCK_SIZE;	/* V1/V2 block size */
+ 	block_size = _STATIC_BLOCK_SIZE;	/* V1/V2 block size */
   }
 
   if(!inodes_per_block)
@@ -508,10 +508,10 @@ ino_t inodes;
 
   zone_size = 1 << zone_shift;	/* nr of blocks per zone */
 
-  if (lseek(fd, (off_t) STATIC_BLOCK_SIZE, SEEK_SET) == (off_t) -1) {
+  if (lseek(fd, (off_t) _STATIC_BLOCK_SIZE, SEEK_SET) == (off_t) -1) {
 	pexit("super() couldn't seek");
   }
-  if (write(fd, buf, STATIC_BLOCK_SIZE) != STATIC_BLOCK_SIZE) {
+  if (write(fd, buf, _STATIC_BLOCK_SIZE) != _STATIC_BLOCK_SIZE) {
 	pexit("super() couldn't write");
   }
 
@@ -1537,8 +1537,8 @@ char *buf;
   	perror("lseek");
   	pexit("seek failed");
   }
-  k = read(fd, buf, STATIC_BLOCK_SIZE);
-  if (k != STATIC_BLOCK_SIZE) {
+  k = read(fd, buf, _STATIC_BLOCK_SIZE);
+  if (k != _STATIC_BLOCK_SIZE) {
 	pexit("get_super_block couldn't read");
   }
 }
diff --git a/commands/simple/mkswap.c b/commands/simple/mkswap.c
index 19a46e473..5211661f3 100755
--- a/commands/simple/mkswap.c
+++ b/commands/simple/mkswap.c
@@ -40,7 +40,7 @@ int main(int argc, char **argv)
     ssize_t r;
     struct super_block super;
     swap_hdr_t swap_hdr;
-    static u8_t block[MAX_BLOCK_SIZE];
+    static u8_t block[_MAX_BLOCK_SIZE];
 
     first= 0;
     i= 1;
@@ -105,7 +105,7 @@ int main(int argc, char **argv)
 	    /* Is there a file system? */
 	    r= -1;
 	    if (lseek(fd, SUPER_BLOCK_BYTES, SEEK_SET) == -1
-		|| (r= read(fd, block, STATIC_BLOCK_SIZE)) < STATIC_BLOCK_SIZE
+		|| (r= read(fd, block, _STATIC_BLOCK_SIZE)) < _STATIC_BLOCK_SIZE
 	    ) {
 		fprintf(stderr, "mkswap: %s: %s\n",
 		    file, r >= 0 ? "End of file" : strerror(errno));
@@ -113,10 +113,10 @@ int main(int argc, char **argv)
 	    }
 	    memcpy(&super, block, sizeof(super));
 	    if (super.s_magic == SUPER_MAGIC) {
-		offset= (unsigned long) super.s_nzones * STATIC_BLOCK_SIZE;
+		offset= (unsigned long) super.s_nzones * _STATIC_BLOCK_SIZE;
 	    } else
 	    if (super.s_magic == SUPER_V2) {
-		offset= (unsigned long) super.s_zones * STATIC_BLOCK_SIZE;
+		offset= (unsigned long) super.s_zones * _STATIC_BLOCK_SIZE;
 	    } else if (super.s_magic == SUPER_V3) {
 		offset= (unsigned long) super.s_zones * super.s_block_size;
 	    } else {
diff --git a/commands/simple/mount.c b/commands/simple/mount.c
index 8fe83842a..cc7119854 100755
--- a/commands/simple/mount.c
+++ b/commands/simple/mount.c
@@ -161,7 +161,7 @@ char *this;
 void swapon(file)
 char *file;
 {
-  u32_t super[2][MAX_BLOCK_SIZE / 2 / sizeof(u32_t)];
+  u32_t super[2][_MAX_BLOCK_SIZE / 2 / sizeof(u32_t)];
   swap_hdr_t *sp;
   struct mmswapon mmswapon;
   int fd, r;
@@ -169,7 +169,7 @@ char *file;
   
   if ((fd = open(file, O_RDWR)) < 0
 	|| lseek(fd, SUPER_BLOCK_BYTES, SEEK_SET) == -1
-	|| (r = read(fd, super, STATIC_BLOCK_SIZE)) < 0
+	|| (r = read(fd, super, _STATIC_BLOCK_SIZE)) < 0
   ) {
 	err = strerror(errno);
 	std_err("mount: ");
@@ -182,7 +182,7 @@ char *file;
   sp = (swap_hdr_t *) &super[0];
   if (memcmp(sp->sh_magic, MAGIC, sizeof(MAGIC)) != 0)
 	sp = (swap_hdr_t *) &super[1];
-  if (r == STATIC_BLOCK_SIZE && memcmp(sp->sh_magic, MAGIC, sizeof(MAGIC)) != 0
+  if (r == _STATIC_BLOCK_SIZE && memcmp(sp->sh_magic, MAGIC, sizeof(MAGIC)) != 0
 			|| sp->sh_version > SH_VERSION) {
 	std_err("mount: ");
 	std_err(file);
diff --git a/commands/simple/readfs.c b/commands/simple/readfs.c
index 2389d1d9d..0d2667a46 100755
--- a/commands/simple/readfs.c
+++ b/commands/simple/readfs.c
@@ -36,7 +36,7 @@
 #include <utime.h>
 #include <dirent.h>
 
-#define BLOCK_SIZE STATIC_BLOCK_SIZE
+#define BLOCK_SIZE _STATIC_BLOCK_SIZE
 
 #include <minix/config.h>
 #include <minix/const.h>
diff --git a/include/dirent.h b/include/dirent.h
index cc0576578..1922f0a20 100755
--- a/include/dirent.h
+++ b/include/dirent.h
@@ -40,21 +40,21 @@ struct _v7_direct {
 /* The block size must be at least 1024 bytes, because otherwise
  * the superblock (at 1024 bytes) overlaps with other filesystem data.
  */
-#define MIN_BLOCK_SIZE		 1024
+#define _MIN_BLOCK_SIZE		 1024
 
 /* The below is allocated in some parts of the system as the largest
  * a filesystem block can be. For instance, the boot monitor allocates
  * 3 of these blocks and has to fit within 64kB, so this can't be
  * increased without taking that into account.
  */
-#define MAX_BLOCK_SIZE		 4096
+#define _MAX_BLOCK_SIZE		 4096
 
 /* This is the block size for the fixed versions of the filesystem (V1/V2) */
-#define STATIC_BLOCK_SIZE	1024
+#define _STATIC_BLOCK_SIZE	1024
 
-#define STATIC_FLEX_PER_BLOCK (STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))
-#define FLEX_PER_V7 (_EXTENT(DIRSIZ) + 1)
-#define FLEX_PER_BLOCK (STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))
+#define _STATIC_FLEX_PER_BLOCK (_STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))
+#define _FLEX_PER_V7 (_EXTENT(DIRSIZ) + 1)
+#define _FLEX_PER_BLOCK (_STATIC_BLOCK_SIZE/sizeof(struct _fl_direct))
 
 /* Definitions for the directory(3) routines: */
 typedef struct {
@@ -63,8 +63,8 @@ typedef struct {
 	short		_count;	/* This many objects in buf */
 	off_t		_pos;	/* Position in directory file */
 	struct _fl_direct  *_ptr;	/* Next slot in buf */
-	struct _fl_direct  _buf[FLEX_PER_BLOCK]; /* One block of a directory file */
-	struct _fl_direct  _v7f[FLEX_PER_V7];	 /* V7 entry transformed to flex */
+	struct _fl_direct  _buf[_FLEX_PER_BLOCK]; /* One block of a directory file */
+	struct _fl_direct  _v7f[_FLEX_PER_V7];	 /* V7 entry transformed to flex */
 } DIR;
 
 #define _DIRENT_NAME_LEN 61
diff --git a/servers/fs/buf.h b/servers/fs/buf.h
index cea6a5b96..a17513683 100644
--- a/servers/fs/buf.h
+++ b/servers/fs/buf.h
@@ -17,19 +17,19 @@
 EXTERN struct buf {
   /* Data portion of the buffer. */
   union {
-    char b__data[MAX_BLOCK_SIZE];		     /* ordinary user data */
+    char b__data[_MAX_BLOCK_SIZE];		     /* ordinary user data */
 /* directory block */
-    struct direct b__dir[NR_DIR_ENTRIES(MAX_BLOCK_SIZE)];    
+    struct direct b__dir[NR_DIR_ENTRIES(_MAX_BLOCK_SIZE)];    
 /* V1 indirect block */
     zone1_t b__v1_ind[V1_INDIRECTS];	     
 /* V2 indirect block */
-    zone_t  b__v2_ind[V2_INDIRECTS(MAX_BLOCK_SIZE)];	     
+    zone_t  b__v2_ind[V2_INDIRECTS(_MAX_BLOCK_SIZE)];	     
 /* V1 inode block */
     d1_inode b__v1_ino[V1_INODES_PER_BLOCK]; 
 /* V2 inode block */
-    d2_inode b__v2_ino[V2_INODES_PER_BLOCK(MAX_BLOCK_SIZE)]; 
+    d2_inode b__v2_ino[V2_INODES_PER_BLOCK(_MAX_BLOCK_SIZE)]; 
 /* bit map block */
-    bitchunk_t b__bitmap[FS_BITMAP_CHUNKS(MAX_BLOCK_SIZE)];  
+    bitchunk_t b__bitmap[FS_BITMAP_CHUNKS(_MAX_BLOCK_SIZE)];  
   } b;
 
   /* Header portion of the buffer. */
diff --git a/servers/fs/const.h b/servers/fs/const.h
index 7d696b5f6..245360591 100644
--- a/servers/fs/const.h
+++ b/servers/fs/const.h
@@ -77,10 +77,10 @@
 #define V1_INODE_SIZE             usizeof (d1_inode)  /* bytes in V1 dsk ino */
 
 /* # zones/indir block */
-#define V1_INDIRECTS (STATIC_BLOCK_SIZE/V1_ZONE_NUM_SIZE)  
+#define V1_INDIRECTS (_STATIC_BLOCK_SIZE/V1_ZONE_NUM_SIZE)  
 
 /* # V1 dsk inodes/blk */
-#define V1_INODES_PER_BLOCK (STATIC_BLOCK_SIZE/V1_INODE_SIZE)
+#define V1_INODES_PER_BLOCK (_STATIC_BLOCK_SIZE/V1_INODE_SIZE)
 
 /* Derived sizes pertaining to the V2 file system. */
 #define V2_ZONE_NUM_SIZE            usizeof (zone_t)  /* # bytes in V2 zone  */
diff --git a/servers/fs/main.c b/servers/fs/main.c
index 3bdd7ebfe..f458252b6 100644
--- a/servers/fs/main.c
+++ b/servers/fs/main.c
@@ -271,7 +271,7 @@ PRIVATE void load_ram(void)
   struct super_block *sp, *dsp;
   block_t b;
   Dev_t image_dev;
-  static char sbbuf[MIN_BLOCK_SIZE];
+  static char sbbuf[_MIN_BLOCK_SIZE];
   int block_size_image, block_size_ram, ramfs_block_size;
   int s;
 
@@ -408,20 +408,20 @@ PRIVATE void load_ram(void)
 
   /* Resize the RAM disk root file system. */
   if (dev_io(DEV_READ, root_dev, FS_PROC_NR,
-  	sbbuf, SUPER_BLOCK_BYTES, MIN_BLOCK_SIZE, 0) != MIN_BLOCK_SIZE) {
+  	sbbuf, SUPER_BLOCK_BYTES, _MIN_BLOCK_SIZE, 0) != _MIN_BLOCK_SIZE) {
   	printf("WARNING: ramdisk read for resizing failed\n");
   }
   dsp = (struct super_block *) sbbuf;
   if (dsp->s_magic == SUPER_V3)
   	ramfs_block_size = dsp->s_block_size;
   else
-  	ramfs_block_size = STATIC_BLOCK_SIZE;
+  	ramfs_block_size = _STATIC_BLOCK_SIZE;
   zones = (ram_size_kb * 1024 / ramfs_block_size) >> sp->s_log_zone_size;
 
   dsp->s_nzones = conv2(sp->s_native, (u16_t) zones);
   dsp->s_zones = conv4(sp->s_native, zones);
   if (dev_io(DEV_WRITE, root_dev, FS_PROC_NR,
-  	sbbuf, SUPER_BLOCK_BYTES, MIN_BLOCK_SIZE, 0) != MIN_BLOCK_SIZE) {
+  	sbbuf, SUPER_BLOCK_BYTES, _MIN_BLOCK_SIZE, 0) != _MIN_BLOCK_SIZE) {
   	printf("WARNING: ramdisk write for resizing failed\n");
   }
 }
diff --git a/servers/fs/super.c b/servers/fs/super.c
index 8849adbae..0d2955802 100644
--- a/servers/fs/super.c
+++ b/servers/fs/super.c
@@ -181,7 +181,7 @@ PUBLIC int get_block_size(dev_t dev)
   }
 
   /* no mounted filesystem? use this block size then. */
-  return MIN_BLOCK_SIZE;
+  return _MIN_BLOCK_SIZE;
 }
 
 /*===========================================================================*
@@ -214,14 +214,14 @@ register struct super_block *sp; /* pointer to a superblock */
   dev_t dev;
   int magic;
   int version, native, r;
-  static char sbbuf[MIN_BLOCK_SIZE];
+  static char sbbuf[_MIN_BLOCK_SIZE];
 
   dev = sp->s_dev;		/* save device (will be overwritten by copy) */
   if (dev == NO_DEV)
   	panic(__FILE__,"request for super_block of NO_DEV", NO_NUM);
   r = dev_io(DEV_READ, dev, FS_PROC_NR,
-  	sbbuf, SUPER_BLOCK_BYTES, MIN_BLOCK_SIZE, 0);
-  if (r != MIN_BLOCK_SIZE) {
+  	sbbuf, SUPER_BLOCK_BYTES, _MIN_BLOCK_SIZE, 0);
+  if (r != _MIN_BLOCK_SIZE) {
   	return EINVAL;
   }
   memcpy(sp, sbbuf, sizeof(*sp));
@@ -265,28 +265,28 @@ register struct super_block *sp; /* pointer to a superblock */
    * hide some of the differences.
    */
   if (version == V1) {
-  	sp->s_block_size = STATIC_BLOCK_SIZE;
+  	sp->s_block_size = _STATIC_BLOCK_SIZE;
 	sp->s_zones = sp->s_nzones;	/* only V1 needs this copy */
 	sp->s_inodes_per_block = V1_INODES_PER_BLOCK;
 	sp->s_ndzones = V1_NR_DZONES;
 	sp->s_nindirs = V1_INDIRECTS;
   } else {
   	if (version == V2)
-  		sp->s_block_size = STATIC_BLOCK_SIZE;
-  	if (sp->s_block_size < MIN_BLOCK_SIZE)
+  		sp->s_block_size = _STATIC_BLOCK_SIZE;
+  	if (sp->s_block_size < _MIN_BLOCK_SIZE)
   		return EINVAL;
 	sp->s_inodes_per_block = V2_INODES_PER_BLOCK(sp->s_block_size);
 	sp->s_ndzones = V2_NR_DZONES;
 	sp->s_nindirs = V2_INDIRECTS(sp->s_block_size);
   }
 
-  if (sp->s_block_size < MIN_BLOCK_SIZE) {
+  if (sp->s_block_size < _MIN_BLOCK_SIZE) {
   	return EINVAL;
   }
-  if (sp->s_block_size > MAX_BLOCK_SIZE) {
+  if (sp->s_block_size > _MAX_BLOCK_SIZE) {
   	printf("Filesystem block size is %d kB; maximum filesystem\n"
  	"block size is %d kB. This limit can be increased by recompiling.\n",
-  	sp->s_block_size/1024, MAX_BLOCK_SIZE/1024);
+  	sp->s_block_size/1024, _MAX_BLOCK_SIZE/1024);
   	return EINVAL;
   }
   if ((sp->s_block_size % 512) != 0) {
diff --git a/servers/fs/write.c b/servers/fs/write.c
index f580cff87..23bd3ad6f 100644
--- a/servers/fs/write.c
+++ b/servers/fs/write.c
@@ -241,6 +241,6 @@ PUBLIC void zero_block(bp)
 register struct buf *bp;	/* pointer to buffer to zero */
 {
 /* Zero a block. */
-  memset(bp->b_data, 0, MAX_BLOCK_SIZE);
+  memset(bp->b_data, 0, _MAX_BLOCK_SIZE);
   bp->b_dirt = DIRTY;
 }