diff --git a/bench/string-accumulate.carp b/bench/string-accumulate.carp
index bd55431..218b191 100644
--- a/bench/string-accumulate.carp
+++ b/bench/string-accumulate.carp
@@ -1,5 +1,5 @@
 (load "Bench.carp")
-(load "git@github.com:carpentry-org/strbuf@0.2.1")
+(load "git@github.com:carpentry-org/strbuf@0.3.0")
 
 ; Build an array of n string chunks of the given size.
 (defn make-chunks [n size]
diff --git a/http-client.carp b/http-client.carp
index ac87d0c..f5d28ea 100644
--- a/http-client.carp
+++ b/http-client.carp
@@ -1,7 +1,7 @@
 (load "git@github.com:carpentry-org/socket@0.2.5")
-(load "git@github.com:carpentry-org/http@0.5.0")
+(load "git@github.com:carpentry-org/http@0.6.0")
 (load "git@github.com:carpentry-org/tls@0.2.1")
-(load "git@github.com:carpentry-org/strbuf@0.2.1")
+(load "git@github.com:carpentry-org/strbuf@0.3.0")
 
 ; Byte-indexed prefix/suffix tests; the core ones measure in bytes but slice
 ; in characters.
@@ -520,8 +520,7 @@ that cares about a truncated body must check `error` afterwards.")
                   (when (String.contains-string? &acc "\r\n\r\n")
                     (set! found true)))))
           (Result.Error _) (set! found true)))
-      (let-do [acc (StringBuf.to-string &sb)]
-        (StringBuf.delete sb)
+      (let [acc (StringBuf.into-string sb)]
         (let [split-pos (String.index-of-string &acc "\r\n\r\n")]
           (if (< split-pos 0)
             (Result.Error (ClientError.Receive @"incomplete HTTP headers"))
@@ -804,8 +803,7 @@ headers first, then either drain the body or hand the stream on.
         (match (ResponseStream.poll s)
           (Maybe.Nothing) (set! done true)
           (Maybe.Just chunk) (StringBuf.append-str &sb &chunk)))
-      (let-do [body (StringBuf.to-string &sb)]
-        (StringBuf.delete sb)
+      (let [body (StringBuf.into-string sb)]
         (match @(ResponseStream.error s)
           (Maybe.Just e) (Result.Error e)
           (Maybe.Nothing) (Result.Success body)))))
diff --git a/src/cookie-jar.carp b/src/cookie-jar.carp
index 5e2096a..07f2199 100644
--- a/src/cookie-jar.carp
+++ b/src/cookie-jar.carp
@@ -198,9 +198,7 @@ if no cookies match. Cookies are serialized longest path first.")
               (when (> i 0) (StringBuf.append-str &sb "; "))
               (StringBuf.append-str &sb
                                     &(Cookie.kv (Array.unsafe-nth &matched i)))))
-          (let-do [s (StringBuf.to-string &sb)]
-            (StringBuf.delete sb)
-            (Maybe.Just s))))))
+          (Maybe.Just (StringBuf.into-string sb))))))
 
   (doc apply-to-headers "adds a Cookie header for matching cookies to the
 headers map. Returns headers unchanged if no cookies match.")
diff --git a/src/multipart.carp b/src/multipart.carp
index 5c2900e..bb73167 100644
--- a/src/multipart.carp
+++ b/src/multipart.carp
@@ -205,4 +205,4 @@ without those characters are emitted unchanged.")
       (StringBuf.append-str &sb boundary)
       (StringBuf.append-str &sb "--")
       (StringBuf.append-crlf &sb)
-      (let-do [result (StringBuf.to-string &sb)] (StringBuf.delete sb) result))))
+      (StringBuf.into-string sb))))