diff --git a/csim.c b/csim.c
index 4e37abe..fb00293 100644
--- a/csim.c
+++ b/csim.c
@@ -208,14 +208,25 @@ long parse_int_arg(char* arg, char opt)
 	char* end;
 	long i = strtol(arg, &end, 0);
 
-	if (*end != '\0' || (!i && opt=='E')) { // associativity can not be zero
+	if (*end != '\0') { // associativity can not be zero
 		printf("Invalid argument \"%s\" for option -%c\n", arg, opt);
 		bad_usage_error();
 	}
 	else if (i < 0) {
-		printf("Argument %ld for option %c too small (must be greater than 0)", i, opt);
+		printf("Argument %s for option -%c too small (must be greater than 0)", arg, opt);
 		exit(1);
 	}
+	else if (opt == 'E') {
+		long long_max = (~0UL)>>1;
+		if (i==0) {
+			printf("Argument for option -E can not be 0\n");
+			exit(1);
+		}
+		else if (i == long_max) {
+			printf("Argument %s for option -E too large (must be less than %ld)\n", arg, long_max);
+			exit(1);
+		}
+	}
 	return i;
 }