diff --git a/src/spell.h b/src/spell.h
index e1ca380..a085b0b 100644
--- a/src/spell.h
+++ b/src/spell.h
@@ -211,9 +211,9 @@
 
 // Values for SP_*ERROR are negative, positive values are used by
 // read_cnt_string().
-#define	SP_TRUNCERROR	-1	// spell file truncated error
-#define	SP_FORMERROR	-2	// format error in spell file
-#define SP_OTHERERROR	-3	// other error while reading spell file
+#define	SP_TRUNCERROR	(-1)	// spell file truncated error
+#define	SP_FORMERROR	(-2)	// format error in spell file
+#define SP_OTHERERROR	(-3)	// other error while reading spell file
 
 /*
  * Structure used in "b_langp", filled from 'spelllang'.