diff --git a/lib/chibi/regexp.scm b/lib/chibi/regexp.scm
index 464da7ba..1440a86a 100644
--- a/lib/chibi/regexp.scm
+++ b/lib/chibi/regexp.scm
@@ -99,8 +99,8 @@
   (%make-regexp-match (make-vector len #f) rx str))
 (define (make-regexp-match-for-rx rx str)
   (make-regexp-match (rx-num-save-indexes rx) rx str))
-(define (regexp-match-num-matches md)
-  (vector-length (regexp-match-matches md)))
+(define (regexp-match-count md)
+  (- (quotient (vector-length (regexp-match-matches md)) 2) 1))
 
 (define (regexp-match-name-offset md name)
   (let lp ((ls (regexp-match-names md)) (first #f))
diff --git a/lib/chibi/regexp.sld b/lib/chibi/regexp.sld
index 05af22b0..4d132b62 100644
--- a/lib/chibi/regexp.sld
+++ b/lib/chibi/regexp.sld
@@ -4,7 +4,7 @@
           regexp-matches regexp-matches? regexp-search
           regexp-replace regexp-replace-all
           regexp-fold regexp-extract regexp-split
-          regexp-match? regexp-match-num-matches
+          regexp-match? regexp-match-count
           regexp-match-submatch regexp-match-submatch/list
           regexp-match->list regexp-match->sexp)
   (import (srfi 33) (srfi 69))