diff --git a/src/core/peg.c b/src/core/peg.c
index 3d035533..5057494a 100644
--- a/src/core/peg.c
+++ b/src/core/peg.c
@@ -1738,7 +1738,7 @@ static Janet cfun_peg_replace_generic(int32_t argc, Janet *argv, int only_one) {
                 trail = i;
             }
             int32_t nexti = (int32_t)(result - c.bytes.bytes);
-            JanetByteView subst = janet_text_substitution(&c.subst, c.bytes.bytes + i, nexti - i);
+            JanetByteView subst = janet_text_substitution(&c.subst, c.bytes.bytes + i, nexti - i, c.s.captures);
             janet_buffer_push_bytes(ret, subst.bytes, subst.len);
             trail = nexti;
             if (nexti == i) nexti++;
@@ -1758,8 +1758,8 @@ JANET_CORE_FN(cfun_peg_replace_all,
               "(peg/replace-all peg subst text &opt start & args)",
               "Replace all matches of `peg` in `text` with `subst`, returning a new buffer. "
               "The peg does not need to make captures to do replacement. "
-              "If `subst` is a function, it will be called once for each match "
-              "and should return the actual replacement text to use.") {
+              "If `subst` is a function, it will be called with the "
+              "matching text followed by any captures.") {
     return cfun_peg_replace_generic(argc, argv, 0);
 }
 
@@ -1767,8 +1767,8 @@ JANET_CORE_FN(cfun_peg_replace,
               "(peg/replace peg repl text &opt start & args)",
               "Replace first match of `peg` in `text` with `subst`, returning a new buffer. "
               "The peg does not need to make captures to do replacement. "
-              "If `subst` is a function, it will be called with the matching text, "
-              "and should return the actual replacement text to use. "
+              "If `subst` is a function, it will be called with the "
+              "matching text followed by any captures. "
               "If no matches are found, returns the input string in a new buffer.") {
     return cfun_peg_replace_generic(argc, argv, 1);
 }
diff --git a/src/core/string.c b/src/core/string.c
index f898bb94..e7957edf 100644
--- a/src/core/string.c
+++ b/src/core/string.c
@@ -397,7 +397,7 @@ JANET_CORE_FN(cfun_string_replace,
         kmp_deinit(&s.kmp);
         return janet_stringv(s.kmp.text, s.kmp.textlen);
     }
-    JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen);
+    JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen, NULL);
     buf = janet_string_begin(s.kmp.textlen - s.kmp.patlen + subst.len);
     safe_memcpy(buf, s.kmp.text, result);
     safe_memcpy(buf + result, subst.bytes, subst.len);
@@ -422,7 +422,7 @@ JANET_CORE_FN(cfun_string_replaceall,
     replacesetup(argc, argv, &s);
     janet_buffer_init(&b, s.kmp.textlen);
     while ((result = kmp_next(&s.kmp)) >= 0) {
-        JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen);
+        JanetByteView subst = janet_text_substitution(&s.subst, s.kmp.text + result, s.kmp.patlen, NULL);
         janet_buffer_push_bytes(&b, s.kmp.text + lastindex, result - lastindex);
         janet_buffer_push_bytes(&b, subst.bytes, subst.len);
         lastindex = result + s.kmp.patlen;
diff --git a/src/core/util.c b/src/core/util.c
index ddbb4515..3c50bc94 100644
--- a/src/core/util.c
+++ b/src/core/util.c
@@ -688,19 +688,32 @@ static JanetByteView to_byte_view(Janet value) {
     return result;
 }
 
-JanetByteView janet_text_substitution(Janet *subst, const uint8_t *bytes, uint32_t len) {
-  switch (janet_type(*subst)) {
-      case JANET_CFUNCTION: {
-          Janet matched = janet_stringv(bytes, len);
-          return to_byte_view(janet_unwrap_cfunction(*subst)(1, &matched));
-      }
-      case JANET_FUNCTION: {
-          Janet matched = janet_stringv(bytes, len);
-          return to_byte_view(janet_call(janet_unwrap_function(*subst), 1, &matched));
-      }
-      default:
-          return memoize_byte_view(subst);
-  }
+JanetByteView janet_text_substitution(
+    Janet *subst,
+    const uint8_t *bytes,
+    uint32_t len,
+    JanetArray *extra_argv) {
+    int32_t extra_argc = extra_argv == NULL ? 0 : extra_argv->count;
+    JanetType type = janet_type(*subst);
+    switch (type) {
+        case JANET_FUNCTION:
+        case JANET_CFUNCTION: {
+            int32_t argc = 1 + extra_argc;
+            Janet *argv = janet_tuple_begin(argc);
+            argv[0] = janet_stringv(bytes, len);
+            for (int32_t i = 0; i < extra_argc; i++) {
+                argv[i + 1] = extra_argv->data[i];
+            }
+            janet_tuple_end(argv);
+            if (type == JANET_FUNCTION) {
+                return to_byte_view(janet_call(janet_unwrap_function(*subst), argc, argv));
+            } else {
+                return to_byte_view(janet_unwrap_cfunction(*subst)(argc, argv));
+            }
+        }
+        default:
+            return memoize_byte_view(subst);
+    }
 }
 
 JanetBinding janet_resolve_ext(JanetTable *env, const uint8_t *sym) {
diff --git a/src/core/util.h b/src/core/util.h
index 2eaf003a..b8f9cc90 100644
--- a/src/core/util.h
+++ b/src/core/util.h
@@ -93,7 +93,11 @@ void janet_buffer_format(
     Janet *argv);
 Janet janet_next_impl(Janet ds, Janet key, int is_interpreter);
 JanetBinding janet_binding_from_entry(Janet entry);
-JanetByteView janet_text_substitution(Janet *subst, const uint8_t *bytes, uint32_t len);
+JanetByteView janet_text_substitution(
+    Janet *subst,
+    const uint8_t *bytes,
+    uint32_t len,
+    JanetArray *extra_args);
 
 /* Registry functions */
 void janet_registry_put(
diff --git a/test/suite0008.janet b/test/suite0008.janet
index 457b69ae..1bec7190 100644
--- a/test/suite0008.janet
+++ b/test/suite0008.janet
@@ -340,6 +340,7 @@ neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
 (check-replacer "aba" "" "ababababababa")
 (check-replacer "aba" string/ascii-upper "ababababababa")
 (check-replacer "aba" 123 "ababababababa")
+
 (assert (= (string (peg/replace-all ~(set "ab") string/ascii-upper "abcaa"))
            "ABcAA")
         "peg/replace-all cfunction")
@@ -347,6 +348,23 @@ neldb\0\0\0\xD8\x05printG\x01\0\xDE\xDE\xDE'\x03\0marshal_tes/\x02
            "abcaa")
         "peg/replace-all function")
 
+(defn peg-test [name f peg subst text expected]
+  (assert (= (string (f peg subst text)) expected) name))
+
+(peg-test "peg/replace has access to captures"
+  peg/replace
+  ~(sequence "." (capture (set "ab")))
+  (fn [str char] (string/format "%s -> %s, " str (string/ascii-upper char)))
+  ".a.b.c"
+  ".a -> A, .b.c")
+
+(peg-test "peg/replace-all has access to captures"
+  peg/replace-all
+  ~(sequence "." (capture (set "ab")))
+  (fn [str char] (string/format "%s -> %s, " str (string/ascii-upper char)))
+  ".a.b.c"
+  ".a -> A, .b -> B, .c")
+
 # Peg bug
 (assert (deep= @[] (peg/match '(any 1) @"")) "peg empty pattern 1")
 (assert (deep= @[] (peg/match '(any 1) (buffer))) "peg empty pattern 2")