diff --git a/common/json_parse.c b/common/json_parse.c
index 7b5c31c81..260e9e1b5 100644
--- a/common/json_parse.c
+++ b/common/json_parse.c
@@ -30,7 +30,7 @@ bool json_to_millionths(const char *buffer, const jsmntok_t *tok,
 
 	*millionths = 0;
 	for (int i = tok->start; i < tok->end; i++) {
-		if (isdigit(buffer[i])) {
+		if (cisdigit(buffer[i])) {
 			has_digits = true;
 			/* Ignore too much precision */
 			if (decimal_places >= 0 && ++decimal_places > 6)
diff --git a/common/splice_script.c b/common/splice_script.c
index 453bc6ca5..fd07c3e22 100644
--- a/common/splice_script.c
+++ b/common/splice_script.c
@@ -503,7 +503,7 @@ char *fmt_splice_script_compiler_error(const tal_t *ctx,
 
 static bool is_whitespace(char c)
 {
-	return isspace(c);
+	return cisspace(c);
 }
 
 static struct splice_script_error *clean_whitespace(const tal_t *ctx,
diff --git a/db/db_sqlite3.c b/db/db_sqlite3.c
index 07ded41f6..171c0e06e 100644
--- a/db/db_sqlite3.c
+++ b/db/db_sqlite3.c
@@ -418,7 +418,7 @@ static const char *find_column_name(const tal_t *ctx,
 {
 	size_t start = 0;
 
-	while (isspace(sqlpart[start]))
+	while (cisspace(sqlpart[start]))
 		start++;
 	*after = strspn(sqlpart + start, "abcdefghijklmnopqrstuvwxyz_0123456789") + start;
 	if (*after == start || !cisspace(sqlpart[*after]))
diff --git a/devtools/onion.c b/devtools/onion.c
index 0d517c15e..ca723afd5 100644
--- a/devtools/onion.c
+++ b/devtools/onion.c
@@ -145,7 +145,7 @@ static void do_decode(int argc, char **argv, const u8 *assocdata)
 	size_t hexlen = strlen(hextemp);
 
 	// trim trailing whitespace
-	while (isspace(hextemp[hexlen-1]))
+	while (cisspace(hextemp[hexlen-1]))
 		hexlen--;
 
 	serialized = tal_hexdata(hextemp, hextemp, hexlen);