diff --git a/src/regexp.c b/src/regexp.c
index 91b8015..b4fe7d7 100644
--- a/src/regexp.c
+++ b/src/regexp.c
@@ -2555,17 +2555,17 @@
 				regc('\t');
 				break;
 			    case CLASS_CNTRL:
-				for (cu = 1; cu <= 255; cu++)
+				for (cu = 1; cu <= 127; cu++)
 				    if (iscntrl(cu))
 					regmbc(cu);
 				break;
 			    case CLASS_DIGIT:
-				for (cu = 1; cu <= 255; cu++)
+				for (cu = 1; cu <= 127; cu++)
 				    if (VIM_ISDIGIT(cu))
 					regmbc(cu);
 				break;
 			    case CLASS_GRAPH:
-				for (cu = 1; cu <= 255; cu++)
+				for (cu = 1; cu <= 127; cu++)
 				    if (isgraph(cu))
 					regmbc(cu);
 				break;