diff --git a/src/main/clojure/clojure/tools/reader.clj b/src/main/clojure/clojure/tools/reader.clj
index 70f212d..ee9d784 100644
--- a/src/main/clojure/clojure/tools/reader.clj
+++ b/src/main/clojure/clojure/tools/reader.clj
@@ -27,6 +27,8 @@
            java.util.regex.Pattern
            (java.util List LinkedList)))
 
+(set! *warn-on-reflection* true)
+
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
 ;; helpers
 ;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
@@ -1022,12 +1024,12 @@
   ([] (read+string (source-logging-push-back-reader *in*)))
   ([stream] (read+string stream true nil))
   ([^SourceLoggingPushbackReader stream eof-error? eof-value]
-   (let [^StringBuilder buf (doto (:buffer @(.source-log-frames stream)) (.setLength 0))
+   (let [^StringBuilder buf (doto ^StringBuilder (:buffer @(.source-log-frames stream)) (.setLength 0))
          o (log-source stream (read stream eof-error? eof-value))
          s (.trim (str buf))]
      [o s]))
   ([opts ^SourceLoggingPushbackReader stream]
-   (let [^StringBuilder buf (doto (:buffer @(.source-log-frames stream)) (.setLength 0))
+   (let [^StringBuilder buf (doto ^StringBuilder (:buffer @(.source-log-frames stream)) (.setLength 0))
          o (log-source stream (read opts stream))
          s (.trim (str buf))]
      [o s])))