diff --git a/src/charset.c b/src/charset.c
index 2ecb96c..ed09bd2 100644
--- a/src/charset.c
+++ b/src/charset.c
@@ -1645,6 +1645,12 @@
 }
 
     int
+vim_isalpha(int c)
+{
+    return vim_islower(c) || vim_isupper(c);
+}
+
+    int
 vim_toupper(int c)
 {
     if (c <= '@')