diff --git a/src/core/commands.c b/src/core/commands.c
index bfe3373c..c2882925 100644
--- a/src/core/commands.c
+++ b/src/core/commands.c
@@ -574,17 +574,17 @@ static int get_cmd_options(char **data, int ignore_unknown,
 			}
 
 			(*data)++;
-			if (**data == '-' && i_isspace((*data)[1])) {
+			if (**data == '-' && (*data)[1] == ' ') {
 				/* -- option means end of options even
 				   if next word starts with - */
 				(*data)++;
-				while (i_isspace(**data)) (*data)++;
+				while (**data == ' ') (*data)++;
 				break;
 			}
 
 			if (**data == '\0')
 				option = "-";
-			else if (!i_isspace(**data))
+			else if (**data != ' ')
 				option = cmd_get_param(data);
 			else {
 				option = "-";
@@ -629,7 +629,7 @@ static int get_cmd_options(char **data, int ignore_unknown,
 			    *optlist[pos] == '!')
 				option = NULL;
 
-			while (i_isspace(**data)) (*data)++;
+			while (**data == ' ') (*data)++;
 			continue;
 		}
 
@@ -647,7 +647,7 @@ static int get_cmd_options(char **data, int ignore_unknown,
 		}
 		option = NULL;
 
-		while (i_isspace(**data)) (*data)++;
+		while (**data == ' ') (*data)++;
 	}
 
 	return 0;
diff --git a/src/fe-common/core/completion.c b/src/fe-common/core/completion.c
index 7a9c9ad3..be8b76c5 100644
--- a/src/fe-common/core/completion.c
+++ b/src/fe-common/core/completion.c
@@ -38,7 +38,7 @@ static int last_want_space, last_line_pos;
         ((c) == ',')
 
 #define isseparator(c) \
-	(i_isspace(c) || isseparator_notspace(c))
+	((c) == ' ' || isseparator_notspace(c))
 
 void chat_completion_init(void);
 void chat_completion_deinit(void);
@@ -530,7 +530,7 @@ static char *line_get_command(const char *line, char **args, int aliases)
 		} else {
 			checkcmd = g_strndup(line, (int) (ptr-line));
 
-			while (i_isspace(*ptr)) ptr++;
+			while (*ptr == ' ') ptr++;
 			cmdargs = ptr;
 		}
 
diff --git a/src/fe-common/core/fe-messages.c b/src/fe-common/core/fe-messages.c
index 31bbbfad..2ae6c0e1 100644
--- a/src/fe-common/core/fe-messages.c
+++ b/src/fe-common/core/fe-messages.c
@@ -67,7 +67,7 @@ char *expand_emphasis(WI_ITEM_REC *item, const char *text)
 
 		/* check that the beginning marker starts a word, and
 		   that the matching end marker ends a word */
-		if ((pos > 0 && !i_isspace(bgn[-1])) || !ishighalnum(bgn[1]))
+		if ((pos > 0 && bgn[-1] != ' ') || !ishighalnum(bgn[1]))
 			continue;
 		if ((end = strchr(bgn+1, *bgn)) == NULL)
 			continue;
diff --git a/src/irc/core/irc.c b/src/irc/core/irc.c
index cf31814c..2c39a77a 100644
--- a/src/irc/core/irc.c
+++ b/src/irc/core/irc.c
@@ -146,19 +146,19 @@ static char *split_nicks(const char *cmd, char **pre, char **nicks, char **post,
 	*pre = g_strdup(cmd);
 	*post = *nicks = NULL;
 	for (p = *pre; *p != '\0'; p++) {
-		if (!i_isspace(*p))
+		if (*p != ' ')
 			continue;
 
 		if (arg == 1) {
 			/* text after nicks */
 			*p++ = '\0';
-			while (i_isspace(*p)) p++;
+			while (*p == ' ') p++;
 			*post = p;
 			break;
 		}
 
 		/* find nicks */
-		while (i_isspace(p[1])) p++;
+		while (p[1] == ' ') p++;
 		if (--arg == 1) {
 			*p = '\0';
 			*nicks = p+1;