diff --git a/include/freetype/freetype.h b/include/freetype/freetype.h
index b70fcd545..b45718301 100644
--- a/include/freetype/freetype.h
+++ b/include/freetype/freetype.h
@@ -2100,7 +2100,7 @@ FT_BEGIN_HEADER
    *
    *   pathname ::
    *     A pointer to an 8-bit file pathname, which must be a C~string (i.e.,
-   *     no NULL bytes except at the very end).  The pointer is not owned by
+   *     no null bytes except at the very end).  The pointer is not owned by
    *     FreeType.
    *
    *   stream ::
@@ -2189,7 +2189,7 @@ FT_BEGIN_HEADER
    * @note:
    *   The `pathname` string should be recognizable as such by a standard
    *   `fopen` call on your system; in particular, this means that `pathname`
-   *   must not contain NULL bytes.  If that is not sufficient to address all
+   *   must not contain null bytes.  If that is not sufficient to address all
    *   file name possibilities (for example, to handle wide character file
    *   names on Windows in UTF-16 encoding) you might use @FT_Open_Face to
    *   pass a memory array or a stream object instead.
diff --git a/src/bdf/bdflib.c b/src/bdf/bdflib.c
index eebdbf85e..fa92fdffa 100644
--- a/src/bdf/bdflib.c
+++ b/src/bdf/bdflib.c
@@ -170,7 +170,7 @@
 
   /* An auxiliary macro to parse properties, to be used in conditionals. */
   /* It behaves like `strncmp' but also tests the following character    */
-  /* whether it is a whitespace or NULL.                                 */
+  /* whether it is a whitespace or null.                                 */
   /* `property' is a constant string of length `n' to compare with.      */
 #define _bdf_strncmp( name, property, n )      \
           ( ft_strncmp( name, property, n ) || \
@@ -346,7 +346,7 @@
     unsigned long  i, u;
 
 
-    if ( list == 0 || list->used == 0 || n == 0 )
+    if ( list == NULL || list->used == 0 || n == 0 )
       return;
 
     if ( n >= list->used )
@@ -377,7 +377,7 @@
 
     *alen = 0;
 
-    if ( list == 0 || list->used == 0 )
+    if ( list == NULL || list->used == 0 )
       return 0;
 
     dp = list->field[0];
@@ -436,7 +436,7 @@
     /* In the original code, if the `separators' parameter is NULL or */
     /* empty, the list is split into individual bytes.  We don't need */
     /* this, so an error is signaled.                                 */
-    if ( separators == 0 || *separators == 0 )
+    if ( separators == NULL || *separators == 0 )
     {
       error = FT_THROW( Invalid_Argument );
       goto Exit;
@@ -504,7 +504,7 @@
     if ( final_empty )
       list->field[list->used++] = (char*)empty;
 
-    list->field[list->used] = 0;
+    list->field[list->used] = NULL;
 
   Exit:
     return error;
@@ -529,7 +529,7 @@
     FT_Error          error  = FT_Err_Ok;
 
 
-    if ( callback == 0 )
+    if ( callback == NULL )
     {
       error = FT_THROW( Invalid_Argument );
       goto Exit;
@@ -697,7 +697,7 @@
     unsigned long  v;
 
 
-    if ( s == 0 || *s == 0 )
+    if ( s == NULL || *s == 0 )
       return 0;
 
     for ( v = 0; sbitset( ddigits, *s ); s++ )
@@ -722,7 +722,7 @@
     long  v, neg;
 
 
-    if ( s == 0 || *s == 0 )
+    if ( s == NULL || *s == 0 )
       return 0;
 
     /* Check for a minus sign. */
@@ -755,7 +755,7 @@
     unsigned short  v;
 
 
-    if ( s == 0 || *s == 0 )
+    if ( s == NULL || *s == 0 )
       return 0;
 
     for ( v = 0; sbitset( ddigits, *s ); s++ )
@@ -780,7 +780,7 @@
     short  v, neg;
 
 
-    if ( s == 0 || *s == 0 )
+    if ( s == NULL || *s == 0 )
       return 0;
 
     /* Check for a minus. */
@@ -883,7 +883,7 @@
     size_t*  propid;
 
 
-    if ( name == 0 || *name == 0 )
+    if ( name == NULL || *name == 0 )
       return 0;
 
     if ( ( propid = ft_hash_str_lookup( name, &(font->proptbl) ) ) == NULL )
@@ -974,7 +974,7 @@
     FT_UNUSED( lineno );        /* only used in debug mode */
 
 
-    if ( font == 0 || font->name == 0 || font->name[0] == 0 )
+    if ( font == NULL || font->name == NULL || font->name[0] == 0 )
     {
       error = FT_THROW( Invalid_Argument );
       goto Exit;
@@ -1182,7 +1182,7 @@
     {
     case BDF_ATOM:
       fp->value.atom = 0;
-      if ( value != 0 && value[0] )
+      if ( value && value[0] )
       {
         if ( FT_STRDUP( fp->value.atom, value ) )
           goto Exit;
@@ -1496,7 +1496,7 @@
       {
         /* Unencoded glyph.  Check whether it should */
         /* be added or not.                          */
-        if ( p->opts->keep_unencoded != 0 )
+        if ( p->opts->keep_unencoded )
         {
           /* Allocate the next unencoded glyph. */
           if ( font->unencoded_used == font->unencoded_size )
@@ -1677,7 +1677,7 @@
 
       /* If the BDF_CORRECT_METRICS flag is set, then adjust the SWIDTH */
       /* value if necessary.                                            */
-      if ( p->opts->correct_metrics != 0 )
+      if ( p->opts->correct_metrics )
       {
         /* Determine the point size of the glyph. */
         unsigned short  sw = (unsigned short)FT_MulDiv(
@@ -1884,7 +1884,7 @@
     /* comments before the STARTFONT line for some reason.                */
     if ( _bdf_strncmp( line, "COMMENT", 7 ) == 0 )
     {
-      if ( p->opts->keep_comments != 0 && p->font != 0 )
+      if ( p->opts->keep_comments && p->font )
       {
         linelen -= 7;
 
@@ -1917,7 +1917,7 @@
       }
 
       p->flags = BDF_START_;
-      font = p->font = 0;
+      font = p->font = NULL;
 
       if ( FT_NEW( font ) )
         goto Exit;
@@ -2176,7 +2176,7 @@
     if ( FT_NEW( p ) )
       goto Exit;
 
-    p->opts   = (bdf_options_t*)( ( opts != 0 ) ? opts : &_bdf_opts );
+    p->opts   = (bdf_options_t*)( opts ? opts : &_bdf_opts );
     p->minlb  = 32767;
     p->size   = stream->size;
     p->memory = memory;  /* only during font creation */
@@ -2188,7 +2188,7 @@
     if ( error )
       goto Fail;
 
-    if ( p->font != 0 )
+    if ( p->font )
     {
       /* If the font is not proportional, set the font's monowidth */
       /* field to the width of the font bounding box.              */
@@ -2269,9 +2269,9 @@
       }
     }
 
-    if ( p->font != 0 )
+    if ( p->font )
     {
-      /* Make sure the comments are NULL terminated if they exist. */
+      /* Make sure the comments are null terminated if they exist. */
       if ( p->font->comments_len > 0 )
       {
         if ( FT_QRENEW_ARRAY( p->font->comments,
@@ -2316,7 +2316,7 @@
     FT_Memory        memory;
 
 
-    if ( font == 0 )
+    if ( font == NULL )
       return;
 
     memory = font->memory;
@@ -2385,7 +2385,7 @@
     size_t*  propid;
 
 
-    if ( font == 0 || font->props_size == 0 || name == 0 || *name == 0 )
+    if ( font == NULL || font->props_size == 0 || name == NULL || *name == 0 )
       return 0;
 
     propid = ft_hash_str_lookup( name, (FT_Hash)font->internal );
diff --git a/src/cff/cffload.c b/src/cff/cffload.c
index 9a9e0b9d8..3e7c971c3 100644
--- a/src/cff/cffload.c
+++ b/src/cff/cffload.c
@@ -400,7 +400,7 @@
 
   /* Allocate a table containing pointers to an index's elements. */
   /* The `pool' argument makes this function convert the index    */
-  /* entries to C-style strings (this is, NULL-terminated).       */
+  /* entries to C-style strings (this is, null-terminated).       */
   static FT_Error
   cff_index_get_pointers( CFF_Index   idx,
                           FT_Byte***  table,
diff --git a/src/cff/cffobjs.c b/src/cff/cffobjs.c
index 4a040462b..3a4d47dbd 100644
--- a/src/cff/cffobjs.c
+++ b/src/cff/cffobjs.c
@@ -689,13 +689,13 @@
 
         /* In Multiple Master CFFs, two SIDs hold the Normalize Design  */
         /* Vector (NDV) and Convert Design Vector (CDV) charstrings,    */
-        /* which may contain NULL bytes in the middle of the data, too. */
+        /* which may contain null bytes in the middle of the data, too. */
         /* We thus access `cff->strings' directly.                      */
         for ( idx = 1; idx < cff->num_strings; idx++ )
         {
           FT_Byte*    s1    = cff->strings[idx - 1];
           FT_Byte*    s2    = cff->strings[idx];
-          FT_PtrDist  s1len = s2 - s1 - 1; /* without the final NULL byte */
+          FT_PtrDist  s1len = s2 - s1 - 1; /* without the final null byte */
           FT_PtrDist  l;
 
 
diff --git a/src/winfonts/winfnt.c b/src/winfonts/winfnt.c
index d590c0a22..4af2f5417 100644
--- a/src/winfonts/winfnt.c
+++ b/src/winfonts/winfnt.c
@@ -885,7 +885,7 @@
       }
       family_size = font->header.file_size - font->header.face_name_offset;
       /* Some broken fonts don't delimit the face name with a final */
-      /* NULL byte -- the frame is erroneously one byte too small.  */
+      /* null byte -- the frame is erroneously one byte too small.  */
       /* We thus allocate one more byte, setting it explicitly to   */
       /* zero.                                                      */
       if ( FT_QALLOC( font->family_name, family_size + 1 ) )