diff --git a/src/regexp.c b/src/regexp.c
index 81ca514..110d76d 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -247,15 +247,15 @@
     done = TRUE;
 }
 
-#define ri_digit(c)	(c < 0x100 && (class_tab[c] & RI_DIGIT))
-#define ri_hex(c)	(c < 0x100 && (class_tab[c] & RI_HEX))
-#define ri_octal(c)	(c < 0x100 && (class_tab[c] & RI_OCTAL))
-#define ri_word(c)	(c < 0x100 && (class_tab[c] & RI_WORD))
-#define ri_head(c)	(c < 0x100 && (class_tab[c] & RI_HEAD))
-#define ri_alpha(c)	(c < 0x100 && (class_tab[c] & RI_ALPHA))
-#define ri_lower(c)	(c < 0x100 && (class_tab[c] & RI_LOWER))
-#define ri_upper(c)	(c < 0x100 && (class_tab[c] & RI_UPPER))
-#define ri_white(c)	(c < 0x100 && (class_tab[c] & RI_WHITE))
+#define ri_digit(c)	((c) < 0x100 && (class_tab[c] & RI_DIGIT))
+#define ri_hex(c)	((c) < 0x100 && (class_tab[c] & RI_HEX))
+#define ri_octal(c)	((c) < 0x100 && (class_tab[c] & RI_OCTAL))
+#define ri_word(c)	((c) < 0x100 && (class_tab[c] & RI_WORD))
+#define ri_head(c)	((c) < 0x100 && (class_tab[c] & RI_HEAD))
+#define ri_alpha(c)	((c) < 0x100 && (class_tab[c] & RI_ALPHA))
+#define ri_lower(c)	((c) < 0x100 && (class_tab[c] & RI_LOWER))
+#define ri_upper(c)	((c) < 0x100 && (class_tab[c] & RI_UPPER))
+#define ri_white(c)	((c) < 0x100 && (class_tab[c] & RI_WHITE))
 
 // flags for regflags
 #define RF_ICASE    1	// ignore case