diff --git a/contrib/dbase/dbf2pg.c b/contrib/dbase/dbf2pg.c
index a635e09122..038c2b5aba 100644
--- a/contrib/dbase/dbf2pg.c
+++ b/contrib/dbase/dbf2pg.c
@@ -78,7 +78,7 @@ isinteger(char *buff)
 				i++;
 				continue;
 			}
-		if (!isdigit((int) *i))
+		if (!isdigit((unsigned char) *i))
 			return 0;
 		i++;
 	}
@@ -90,7 +90,7 @@ strtoupper(char *string)
 {
 	while (*string != '\0')
 	{
-		*string = toupper(*string);
+		*string = toupper((unsigned char) *string);
 		string++;
 	}
 }
@@ -100,7 +100,7 @@ strtolower(char *string)
 {
 	while (*string != '\0')
 	{
-		*string = tolower(*string);
+		*string = tolower((unsigned char) *string);
 		string++;
 	}
 }
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch.c b/contrib/fuzzystrmatch/fuzzystrmatch.c
index 3f863a4fa9..fbb16f66b3 100644
--- a/contrib/fuzzystrmatch/fuzzystrmatch.c
+++ b/contrib/fuzzystrmatch/fuzzystrmatch.c
@@ -253,17 +253,18 @@ metaphone(PG_FUNCTION_ARGS)
  * accesssing the array directly... */
 
 /* Look at the next letter in the word */
-#define Next_Letter (toupper(word[w_idx+1]))
+#define Next_Letter (toupper((unsigned char) word[w_idx+1]))
 /* Look at the current letter in the word */
-#define Curr_Letter (toupper(word[w_idx]))
+#define Curr_Letter (toupper((unsigned char) word[w_idx]))
 /* Go N letters back. */
-#define Look_Back_Letter(n) (w_idx >= n ? toupper(word[w_idx-n]) : '\0')
+#define Look_Back_Letter(n) \
+	(w_idx >= (n) ? toupper((unsigned char) word[w_idx-(n)]) : '\0')
 /* Previous letter.  I dunno, should this return null on failure? */
 #define Prev_Letter (Look_Back_Letter(1))
 /* Look two letters down.  It makes sure you don't walk off the string. */
-#define After_Next_Letter	(Next_Letter != '\0' ? toupper(word[w_idx+2]) \
-												 : '\0')
-#define Look_Ahead_Letter(n) (toupper(Lookahead(word+w_idx, n)))
+#define After_Next_Letter \
+	(Next_Letter != '\0' ? toupper((unsigned char) word[w_idx+2]) : '\0')
+#define Look_Ahead_Letter(n) toupper((unsigned char) Lookahead(word+w_idx, n))
 
 
 /* Allows us to safely look ahead an arbitrary # of letters */
@@ -291,7 +292,7 @@ Lookahead(char *word, int how_far)
 #define Phone_Len	(p_idx)
 
 /* Note is a letter is a 'break' in the word */
-#define Isbreak(c)	(!isalpha(c))
+#define Isbreak(c)	(!isalpha((unsigned char) (c)))
 
 
 int
@@ -336,7 +337,7 @@ _metaphone(
 
 	/*-- The first phoneme has to be processed specially. --*/
 	/* Find our first letter */
-	for (; !isalpha(Curr_Letter); w_idx++)
+	for (; !isalpha((unsigned char) (Curr_Letter)); w_idx++)
 	{
 		/* On the off chance we were given nothing but crap... */
 		if (Curr_Letter == '\0')
@@ -435,7 +436,7 @@ _metaphone(
 		 */
 
 		/* Ignore non-alphas */
-		if (!isalpha(Curr_Letter))
+		if (!isalpha((unsigned char) (Curr_Letter)))
 			continue;
 
 		/* Drop duplicates, except CC */
diff --git a/contrib/fuzzystrmatch/fuzzystrmatch.h b/contrib/fuzzystrmatch/fuzzystrmatch.h
index 23e5e57d92..59e0d9258c 100644
--- a/contrib/fuzzystrmatch/fuzzystrmatch.h
+++ b/contrib/fuzzystrmatch/fuzzystrmatch.h
@@ -153,7 +153,7 @@ char		_codes[26] = {
 };
 
 
-#define ENCODE(c) (isalpha(c) ? _codes[((toupper(c)) - 'A')] : 0)
+#define ENCODE(c) (isalpha((unsigned char) (c)) ? _codes[((toupper((unsigned char) (c))) - 'A')] : 0)
 
 #define isvowel(c)	(ENCODE(c) & 1)		/* AEIOU */
 
diff --git a/contrib/pgcrypto/pgcrypto.c b/contrib/pgcrypto/pgcrypto.c
index bf700e3da9..d3dc36dc9a 100644
--- a/contrib/pgcrypto/pgcrypto.c
+++ b/contrib/pgcrypto/pgcrypto.c
@@ -26,7 +26,7 @@
  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  * SUCH DAMAGE.
  *
- * $Id: pgcrypto.c,v 1.11 2001/11/20 15:50:53 momjian Exp $
+ * $Id: pgcrypto.c,v 1.12 2001/12/30 23:09:41 tgl Exp $
  */
 
 #include <postgres.h>
@@ -556,7 +556,7 @@ find_provider(text *name,
 
 	p = VARDATA(name);
 	for (i = 0; i < len; i++)
-		buf[i] = tolower(p[i]);
+		buf[i] = tolower((unsigned char) p[i]);
 	buf[len] = 0;
 
 	err = provider_lookup(buf, &res);
diff --git a/src/backend/utils/adt/datetime.c b/src/backend/utils/adt/datetime.c
index 674eaeb91a..49e93abe99 100644
--- a/src/backend/utils/adt/datetime.c
+++ b/src/backend/utils/adt/datetime.c
@@ -8,7 +8,7 @@
  *
  *
  * IDENTIFICATION
- *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.85 2001/12/29 21:28:18 momjian Exp $
+ *	  $Header: /cvsroot/pgsql/src/backend/utils/adt/datetime.c,v 1.86 2001/12/30 23:09:41 tgl Exp $
  *
  *-------------------------------------------------------------------------
  */
@@ -959,7 +959,7 @@ DecodeDateTime(char **field, int *ftype, int nf,
 					if (tzp == NULL)
 						return -1;
 
-					if (isdigit(*field[i]) || ptype != 0)
+					if (isdigit((unsigned char) *field[i]) || ptype != 0)
 					{
 						char *cp;
 
@@ -1573,7 +1573,7 @@ DecodeTimeOnly(char **field, int *ftype, int nf,
 				/* otherwise, this is a time and/or time zone */
 				else
 				{
-					if (isdigit(*field[i]))
+					if (isdigit((unsigned char) *field[i]))
 					{
 						char *cp;
 
diff --git a/src/interfaces/odbc/connection.c b/src/interfaces/odbc/connection.c
index e39501f800..e057d7b73f 100644
--- a/src/interfaces/odbc/connection.c
+++ b/src/interfaces/odbc/connection.c
@@ -1092,7 +1092,7 @@ CC_send_query(ConnectionClass *self, char *query, QueryInfo *qi)
 
 	ReadyToReturn = FALSE;
 	empty_reqs = 0;
-	for (wq = query; isspace(*wq); wq++)
+	for (wq = query; isspace((unsigned char) *wq); wq++)
 		;
 	if (*wq == '\0')
 		empty_reqs = 1;
diff --git a/src/interfaces/odbc/convert.c b/src/interfaces/odbc/convert.c
index 57bf6b70df..0b609a07db 100644
--- a/src/interfaces/odbc/convert.c
+++ b/src/interfaces/odbc/convert.c
@@ -193,7 +193,7 @@ timestamp2stime(const char *str, SIMPLE_TIME *st, BOOL *bZone, int *zone)
 			}
 			for (i = 1; i < 10; i++)
 			{
-				if (!isdigit(rest[i]))
+				if (!isdigit((unsigned char) rest[i]))
 					break;
 			}
 			for (; i < 10; i++)
@@ -1351,7 +1351,7 @@ copy_statement_with_parameters(StatementClass *stmt)
 					while (isspace((unsigned char) old_statement[++opos]));
 				}
 				if (strnicmp(&old_statement[opos], "call", lit_call_len) ||
-					!isspace(old_statement[opos + lit_call_len]))
+					!isspace((unsigned char) old_statement[opos + lit_call_len]))
 				{
 					opos--;
 					continue;
@@ -1407,7 +1407,7 @@ copy_statement_with_parameters(StatementClass *stmt)
 				in_dquote = TRUE;
 			else
 			{
-				if (isspace(oldchar))
+				if (isspace((unsigned char) oldchar))
 				{
 					if (!prev_token_end)
 					{