diff --git a/lib/misc.c b/lib/misc.c
index 31c44a3..1d20e1b 100644
--- a/lib/misc.c
+++ b/lib/misc.c
@@ -79,7 +79,7 @@
 int parse_area_spec(const char *str, loff_t *start, loff_t *size)
 {
 	char *endp;
-	loff_t end, _start;
+	loff_t end, _start, _size;
 
 	if (!isdigit(*str))
 		return -1;
@@ -90,7 +90,7 @@
 
 	if (!*str) {
 		/* beginning given, but no size, assume maximum size */
-		*size = ~0;
+		_size = ~0;
 		goto success;
 	}
 
@@ -99,12 +99,13 @@
 		if (!isdigit(*(str + 1)))
 			return -1;
 
-		end = strtoull_suffix(str + 1, NULL, 0);
+		end = strtoull_suffix(str + 1, &endp, 0);
+		str = endp;
 		if (end < _start) {
 			printf("end < start\n");
 			return -1;
 		}
-		*size = end - _start + 1;
+		_size = end - _start + 1;
 		goto success;
 	}
 
@@ -113,14 +114,18 @@
 		if (!isdigit(*(str + 1)))
 			return -1;
 
-		*size = strtoull_suffix(str + 1, NULL, 0);
+		_size = strtoull_suffix(str + 1, &endp, 0);
+		str = endp;
 		goto success;
 	}
 
 	return -1;
 
 success:
+	if (*str && !isspace(*str))
+		return -1;
 	*start = _start;
+	*size = _size;
 	return 0;
 }
 EXPORT_SYMBOL(parse_area_spec);