diff --git a/common/cut.c b/common/cut.c
index 11db42fb..845f28c3 100644
--- a/common/cut.c
+++ b/common/cut.c
@@ -72,7 +72,7 @@ cut(
 	int flags)
 {
 	CB *cbp;
-	CHAR_T name = '\0';
+	CHAR_T name = L('\0');
 	recno_t lno;
 	int append, copy_one, copy_def;
 
@@ -106,10 +106,10 @@ cut(
 			copy_one = 1;
 			cb_rotate(sp);
 		}
-		if ((append = isupper(name))) {
+		if ((append = ISUPPER(name))) {
 			if (!copy_one)
 				copy_def = 1;
-			name = tolower(name);
+			name = TOLOWER(name);
 		}
 namecb:		CBNAME(sp, cbp, name);
 	} else if (LF_ISSET(CUT_NUMREQ) || (LF_ISSET(CUT_NUMOPT) &&
diff --git a/common/cut.h b/common/cut.h
index 30e9350d..5f633bd7 100644
--- a/common/cut.h
+++ b/common/cut.h
@@ -67,7 +67,7 @@ struct _text {				/* Text: a linked list of lines. */
  */
 #define	CBNAME(sp, cbp, nch) {						\
 	CHAR_T L__name;							\
-	L__name = isupper(nch) ? tolower(nch) : (nch);			\
+	L__name = ISUPPER(nch) ? TOLOWER(nch) : (nch);			\
 	SLIST_FOREACH(cbp, sp->gp->cutq, q)				\
 		if (cbp->name == L__name)				\
 			break;						\
diff --git a/ex/ex.c b/ex/ex.c
index 326a9f2b..ec3281da 100644
--- a/ex/ex.c
+++ b/ex/ex.c
@@ -429,7 +429,7 @@ loop:	ecp = SLIST_FIRST(gp->ecq);
 			break;
 		case 'E': case 'F': case 'N': case 'P': case 'T': case 'V':
 			newscreen = 1;
-			p[0] = tolower(p[0]);
+			p[0] = TOLOWER(p[0]);
 			break;
 		}
 
@@ -477,7 +477,7 @@ loop:	ecp = SLIST_FIRST(gp->ecq);
 				/* FALLTHROUGH */
 			default:
 unknown:			if (newscreen)
-					p[0] = toupper(p[0]);
+					p[0] = TOUPPER(p[0]);
 				ex_unknown(sp, p, namelen);
 				goto err;
 			}
diff --git a/ex/ex_cscope.c b/ex/ex_cscope.c
index 3440237b..79a6aba3 100644
--- a/ex/ex_cscope.c
+++ b/ex/ex_cscope.c
@@ -125,18 +125,18 @@ ex_cscope(SCR *sp, EXCMD *cmdp)
 
 	/* Skip leading whitespace. */
 	for (p = cmdp->argv[0]->bp, i = cmdp->argv[0]->len; i > 0; --i, ++p)
-		if (!isspace(*p))
+		if (!ISSPACE(*p))
 			break;
 	if (i == 0)
 		goto usage;
 
 	/* Skip the command to any arguments. */
 	for (cmd = p; i > 0; --i, ++p)
-		if (isspace(*p))
+		if (ISSPACE(*p))
 			break;
-	if (*p != '\0') {
-		*p++ = '\0';
-		for (; *p && isspace(*p); ++p);
+	if (*p != L('\0')) {
+		*p++ = L('\0');
+		for (; *p && ISSPACE(*p); ++p);
 	}
 
 	INT2CHAR(sp, cmd, STRLEN(cmd) + 1, np, nlen);
diff --git a/ex/ex_display.c b/ex/ex_display.c
index 6142a44a..9e9c5c7f 100644
--- a/ex/ex_display.c
+++ b/ex/ex_display.c
@@ -94,7 +94,7 @@ bdisplay(SCR *sp)
 
 	/* Display regular cut buffers. */
 	SLIST_FOREACH(cbp, sp->gp->cutq, q) {
-		if (isdigit(cbp->name))
+		if (ISDIGIT(cbp->name))
 			continue;
 		if (!TAILQ_EMPTY(cbp->textq))
 			db(sp, cbp, NULL);
@@ -103,7 +103,7 @@ bdisplay(SCR *sp)
 	}
 	/* Display numbered buffers. */
 	SLIST_FOREACH(cbp, sp->gp->cutq, q) {
-		if (!isdigit(cbp->name))
+		if (!ISDIGIT(cbp->name))
 			continue;
 		if (!TAILQ_EMPTY(cbp->textq))
 			db(sp, cbp, NULL);
diff --git a/ex/ex_join.c b/ex/ex_join.c
index 082faf9a..d63ffef0 100644
--- a/ex/ex_join.c
+++ b/ex/ex_join.c
@@ -37,7 +37,8 @@ ex_join(SCR *sp, EXCMD *cmdp)
 {
 	recno_t from, to;
 	size_t blen, clen, len, tlen;
-	int echar = 0, extra, first;
+	CHAR_T echar = 0;
+	int extra, first;
 	CHAR_T *bp, *tbp = NULL;
 	CHAR_T *p;
 
@@ -104,8 +105,8 @@ ex_join(SCR *sp, EXCMD *cmdp)
 		 */
 		extra = 0;
 		if (!first && !FL_ISSET(cmdp->iflags, E_C_FORCE)) {
-			if (isblank(echar))
-				for (; len && isblank(*p); --len, ++p);
+			if (ISBLANK(echar))
+				for (; len && ISBLANK(*p); --len, ++p);
 			else if (p[0] != ')') {
 				if (STRCHR(L(".?!"), echar)) {
 					*tbp++ = ' ';
@@ -114,7 +115,7 @@ ex_join(SCR *sp, EXCMD *cmdp)
 				}
 				*tbp++ = ' ';
 				++clen;
-				for (; len && isblank(*p); --len, ++p);
+				for (; len && ISBLANK(*p); --len, ++p);
 			}
 		}
 
diff --git a/ex/ex_map.c b/ex/ex_map.c
index 60dbfe07..bc72608e 100644
--- a/ex/ex_map.c
+++ b/ex/ex_map.c
@@ -70,8 +70,8 @@ ex_map(SCR *sp, EXCMD *cmdp)
 	 * call it as well.  Note, the SEQ_FUNCMAP type is persistent across
 	 * screen types, maybe the next screen type will get it right.
 	 */
-	if (input[0] == '#' && isdigit(input[1])) {
-		for (p = input + 2; isdigit(*p); ++p);
+	if (input[0] == L('#') && ISDIGIT(input[1])) {
+		for (p = input + 2; ISDIGIT(*p); ++p);
 		if (p[0] != '\0')
 			goto nofunc;
 
diff --git a/vi/v_increment.c b/vi/v_increment.c
index 0a121a91..2a7c7d83 100644
--- a/vi/v_increment.c
+++ b/vi/v_increment.c
@@ -127,13 +127,13 @@ v_increment(SCR *sp, VICMD *vp)
 		base = 10;
 		end = beg + 1;
 		ntype = fmt[SDEC];
-		if (!isdigit(p[end]))
+		if (!ISDIGIT(p[end]))
 			goto nonum;
 	} else {
 decimal:	base = 10;
 		end = beg;
 		ntype = fmt[DEC];
-		if (!isdigit(p[end])) {
+		if (!ISDIGIT(p[end])) {
 nonum:			msgq(sp, M_ERR, "181|Cursor not in a number");
 			return (1);
 		}
@@ -152,7 +152,7 @@ nonum:			msgq(sp, M_ERR, "181|Cursor not in a number");
 			}
 			break;
 		case 10:
-			if (isdigit(p[end]))
+			if (ISDIGIT(p[end]))
 				continue;
 			break;
 		case 16:
diff --git a/vi/v_match.c b/vi/v_match.c
index 2fae58e3..2e36f4de 100644
--- a/vi/v_match.c
+++ b/vi/v_match.c
@@ -144,7 +144,7 @@ nomatch:		msgq(sp, M_BERR, "184|No match character on this line");
 	if (db_get(sp, mp->lno, DBG_FATAL, &p, &len))
 		return (1);
 	for (p += mp->cno + 1, len -= mp->cno; --len; ++p)
-		if (!isblank(*p))
+		if (!ISBLANK(*p))
 			return (0);
 	F_SET(vp, VM_LMODE);
 	return (0);
diff --git a/vi/v_replace.c b/vi/v_replace.c
index 2a7ea979..d95c2997 100644
--- a/vi/v_replace.c
+++ b/vi/v_replace.c
@@ -172,7 +172,7 @@ next:		if (v_event_get(sp, &ev, 0, 0))
 		p += vp->m_start.cno + cnt;
 		len -= vp->m_start.cno + cnt;
 		if (len != 0 && O_ISSET(sp, O_AUTOINDENT))
-			for (; len && isblank(*p); --len, ++p);
+			for (; len && ISBLANK(*p); --len, ++p);
 
 		if ((tp = text_init(sp, p, len, len)) == NULL)
 			goto err_ret;
diff --git a/vi/v_search.c b/vi/v_search.c
index 1d6b2603..690fd1a2 100644
--- a/vi/v_search.c
+++ b/vi/v_search.c
@@ -224,10 +224,11 @@ v_exaddr(SCR *sp, VICMD *vp, dir_t dir)
 
 		/* No blanks, just like the z command. */
 		for (t = cmd + 1, tlen = len - 1; tlen > 0; ++t, --tlen)
-			if (!isdigit(*t))
+			if (!ISDIGIT(*t))
 				break;
 		if (tlen &&
-		    (*t == '-' || *t == '.' || *t == '+' || *t == '^')) {
+		    (*t == L('-') || *t == L('.') || *t == L('+') ||
+		     *t == L('^'))) {
 			++t;
 			--tlen;
 			type = 1;
diff --git a/vi/v_sentence.c b/vi/v_sentence.c
index ddbc6c70..85f14cb5 100644
--- a/vi/v_sentence.c
+++ b/vi/v_sentence.c
@@ -72,7 +72,7 @@ v_sentencef(SCR *sp, VICMD *vp)
 	 * This may not handle "  .  " correctly, but it's real unclear
 	 * what correctly means in that case.
 	 */
-	if (cs.cs_flags == CS_EMP || (cs.cs_flags == 0 && isblank(cs.cs_ch))) {
+	if (cs.cs_flags == CS_EMP || (cs.cs_flags == 0 && ISBLANK(cs.cs_ch))) {
 		if (cs_fblank(sp, &cs))
 			return (1);
 		if (--cnt == 0) {
@@ -93,7 +93,7 @@ v_sentencef(SCR *sp, VICMD *vp)
 				if (cs_next(sp, &cs))
 					return (1);
 				if (cs.cs_flags == 0 &&
-				    isblank(cs.cs_ch) && cs_fblank(sp, &cs))
+				    ISBLANK(cs.cs_ch) && cs_fblank(sp, &cs))
 					return (1);
 				goto okret;
 			}
@@ -233,11 +233,11 @@ v_sentenceb(SCR *sp, VICMD *vp)
 			if (cs.cs_flags != CS_EOL)
 				break;
 		}
-	} else if (cs.cs_flags == 0 && !isblank(cs.cs_ch))
+	} else if (cs.cs_flags == 0 && !ISBLANK(cs.cs_ch))
 		for (;;) {
 			if (cs_prev(sp, &cs))
 				return (1);
-			if (cs.cs_flags != 0 || isblank(cs.cs_ch))
+			if (cs.cs_flags != 0 || ISBLANK(cs.cs_ch))
 				break;
 		}
 
@@ -280,7 +280,7 @@ ret:			slno = cs.cs_lno;
 			} while (!cs.cs_flags &&
 			    (cs.cs_ch == ')' || cs.cs_ch == ']' ||
 			    cs.cs_ch == '"' || cs.cs_ch == '\''));
-			if ((cs.cs_flags || isblank(cs.cs_ch)) &&
+			if ((cs.cs_flags || ISBLANK(cs.cs_ch)) &&
 			    cs_fblank(sp, &cs))
 				return (1);
 
@@ -303,7 +303,7 @@ ret:			slno = cs.cs_lno;
 					return (1);
 				if (cs.cs_flags == CS_EOL)
 					continue;
-				if (cs.cs_flags == 0 && isblank(cs.cs_ch))
+				if (cs.cs_flags == 0 && ISBLANK(cs.cs_ch))
 					continue;
 				break;
 			}
@@ -321,7 +321,7 @@ ret:			slno = cs.cs_lno;
 			break;
 		default:
 			last =
-			    cs.cs_flags == CS_EOL || isblank(cs.cs_ch) ||
+			    cs.cs_flags == CS_EOL || ISBLANK(cs.cs_ch) ||
 			    cs.cs_ch == ')' || cs.cs_ch == ']' ||
 			    cs.cs_ch == '"' || cs.cs_ch == '\'' ? 1 : 0;
 		}
diff --git a/vi/v_txt.c b/vi/v_txt.c
index 1348b278..25a9b6d8 100644
--- a/vi/v_txt.c
+++ b/vi/v_txt.c
@@ -749,16 +749,16 @@ k_cr:		if (LF_ISSET(TXT_CR)) {
 		owrite = tp->owrite;
 		insert = tp->insert;
 		if (LF_ISSET(TXT_REPLACE) && owrite != 0) {
-			for (p = tp->lb + tp->cno; owrite > 0 && isblank(*p);
+			for (p = tp->lb + tp->cno; owrite > 0 && ISBLANK(*p);
 			    ++p, --owrite, ++tp->R_erase);
 			if (owrite == 0)
-				for (; insert > 0 && isblank(*p);
+				for (; insert > 0 && ISBLANK(*p);
 				    ++p, ++tp->R_erase, --insert);
 		} else {
 			p = tp->lb + tp->cno + owrite;
 			if (O_ISSET(sp, O_AUTOINDENT))
 				for (; insert > 0 &&
-				    isblank(*p); ++p, --insert);
+				    ISBLANK(*p); ++p, --insert);
 			owrite = 0;
 		}
 
@@ -1291,7 +1291,7 @@ leftmargin:		tp->lb[tp->cno - 1] = ' ';
 					goto resolve;
 				}
 			}
-			if (isblank(evp->e_c) && UNMAP_TST)
+			if (ISBLANK(evp->e_c) && UNMAP_TST)
 				txt_unmap(sp, tp, &ec_flags);
 		}
 		if (abb != AB_NOTSET)
@@ -1341,7 +1341,7 @@ insl_ch:	if (txt_insch(sp, tp, &evp->e_c, flags))
 				if (txt_margin(sp, tp, &wmt, &tmp, flags))
 					goto err;
 				if (tmp) {
-					if (isblank(evp->e_c))
+					if (ISBLANK(evp->e_c))
 						wm_skip = 1;
 					wm_set = 1;
 					goto k_cr;
@@ -1507,7 +1507,7 @@ txt_abbrev(SCR *sp, TEXT *tp, CHAR_T *pushcp, int isinfoline, int *didsubp, int
 	off = tp->cno - 1;			/* Previous character. */
 	p = tp->lb + off;
 	len = 1;				/* One character test. */
-	if (off == tp->offset || isblank(p[-1]))
+	if (off == tp->offset || ISBLANK(p[-1]))
 		goto search;
 	if (inword(p[-1]))			/* Move backward to change. */
 		for (;;) {
@@ -1519,7 +1519,7 @@ txt_abbrev(SCR *sp, TEXT *tp, CHAR_T *pushcp, int isinfoline, int *didsubp, int
 		for (;;) {
 			--off; --p; ++len;
 			if (off == tp->offset ||
-			    inword(p[-1]) || isblank(p[-1]))
+			    inword(p[-1]) || ISBLANK(p[-1]))
 				break;
 		}
 
@@ -1643,7 +1643,7 @@ txt_unmap(SCR *sp, TEXT *tp, u_int32_t *ec_flagsp)
 
 	/* Find the beginning of this "word". */
 	for (off = tp->cno - 1, p = tp->lb + off, len = 0;; --p, --off) {
-		if (isblank(*p)) {
+		if (ISBLANK(*p)) {
 			++p;
 			break;
 		}
@@ -1710,7 +1710,7 @@ txt_ai_resolve(SCR *sp, TEXT *tp, int *changedp)
 
 	/* Figure out the last <blank> screen column. */
 	for (p = tp->lb, scno = 0, len = tp->len,
-	    spaces = tab_after_sp = 0; len-- && isblank(*p); ++p)
+	    spaces = tab_after_sp = 0; len-- && ISBLANK(*p); ++p)
 		if (*p == '\t') {
 			if (spaces)
 				tab_after_sp = 1;
@@ -1785,7 +1785,7 @@ v_txt_auto(SCR *sp, recno_t lno, TEXT *aitp, size_t len, TEXT *tp)
 
 	/* Count whitespace characters. */
 	for (p = t; len > 0; ++p, --len)
-		if (!isblank(*p))
+		if (!ISBLANK(*p))
 			break;
 
 	/* Set count, check for no indentation. */
@@ -2794,7 +2794,7 @@ txt_margin(SCR *sp, TEXT *tp, TEXT *wmtp, int *didbreak, u_int32_t flags)
 
 	/* Find the nearest previous blank. */
 	for (off = tp->cno - 1, p = tp->lb + off, len = 0;; --off, --p, ++len) {
-		if (isblank(*p)) {
+		if (ISBLANK(*p)) {
 			wp = p + 1;
 			break;
 		}
@@ -2846,7 +2846,7 @@ txt_margin(SCR *sp, TEXT *tp, TEXT *wmtp, int *didbreak, u_int32_t flags)
 	 * Delete any trailing whitespace from the current line.
 	 */
 	for (;; --p, --off) {
-		if (!isblank(*p))
+		if (!ISBLANK(*p))
 			break;
 		--tp->cno;
 		--tp->len;
diff --git a/vi/v_util.c b/vi/v_util.c
index 6348ca73..ee796701 100644
--- a/vi/v_util.c
+++ b/vi/v_util.c
@@ -123,7 +123,7 @@ int
 v_isempty(CHAR_T *p, size_t len)
 {
 	for (; len--; ++p)
-		if (!isblank(*p))
+		if (!ISBLANK(*p))
 			return (0);
 	return (1);
 }