diff --git a/src/MessageReader.cpp b/src/MessageReader.cpp
index 0ab633ab30..8ba5ebdb79 100644
--- a/src/MessageReader.cpp
+++ b/src/MessageReader.cpp
@@ -141,9 +141,9 @@ bool MessageReader::Run() {
       if (!Read16(&uid)) return false;
       unsigned long size;
       if (!ReadUleb128(&size)) return false;
-      char* params;
+      const char* params;
       if (!Read(&params, size)) return false;
-      m_handler.GotExecuteRpc(id, uid, params, size);
+      m_handler.GotExecuteRpc(id, uid, llvm::StringRef(params, size));
       break;
     }
     case NT_MSG_RPC_RESPONSE: {
@@ -156,9 +156,9 @@ bool MessageReader::Run() {
       if (!Read16(&uid)) return false;
       unsigned long size;
       if (!ReadUleb128(&size)) return false;
-      char* results;
+      const char* results;
       if (!Read(&results, size)) return false;
-      m_handler.GotRpcResponse(id, uid, results, size);
+      m_handler.GotRpcResponse(id, uid, llvm::StringRef(results, size));
       break;
     }
     default:
diff --git a/src/MessageReader.h b/src/MessageReader.h
index 3c8e183885..f02664b02f 100644
--- a/src/MessageReader.h
+++ b/src/MessageReader.h
@@ -37,9 +37,9 @@ class MessageHandler {
   virtual void GotEntryDelete(unsigned int id) = 0;
   virtual void GotClearEntries() = 0;
   virtual void GotExecuteRpc(unsigned int id, unsigned int uid,
-                             const char* params, std::size_t params_len) = 0;
+                             llvm::StringRef params) = 0;
   virtual void GotRpcResponse(unsigned int id, unsigned int uid,
-                              const char* results, std::size_t results_len) = 0;
+                              llvm::StringRef results) = 0;
 
   MessageHandler() = default;
   MessageHandler(const MessageHandler&) = delete;
diff --git a/src/WireDecoder.cpp b/src/WireDecoder.cpp
index fda46eeaad..8682c997a9 100644
--- a/src/WireDecoder.cpp
+++ b/src/WireDecoder.cpp
@@ -17,7 +17,7 @@
 
 using namespace ntimpl;
 
-static double ReadDouble(char*& buf) {
+static double ReadDouble(const char*& buf) {
   // Fast but non-portable!
   std::uint64_t val = (*((unsigned char*)buf)) & 0xff;
   ++buf;
@@ -57,7 +57,7 @@ WireDecoder::WireDecoder(raw_istream& is, unsigned int proto_rev) : m_is(is) {
 WireDecoder::~WireDecoder() { std::free(m_buf); }
 
 bool WireDecoder::ReadDouble(double* val) {
-  char* buf;
+  const char* buf;
   if (!Read(&buf, 8)) return false;
   *val = ::ReadDouble(buf);
   return true;
@@ -139,7 +139,7 @@ bool WireDecoder::ReadValue(NT_Type type, NT_Value* value) {
       value->data.arr_boolean.size = size;
 
       // array values
-      char* buf;
+      const char* buf;
       if (!Read(&buf, size)) return false;
       value->data.arr_boolean.arr =
           static_cast<int*>(std::malloc(size * sizeof(int)));
@@ -154,7 +154,7 @@ bool WireDecoder::ReadValue(NT_Type type, NT_Value* value) {
       value->data.arr_double.size = size;
 
       // array values
-      char* buf;
+      const char* buf;
       if (!Read(&buf, size * 8)) return false;
       value->data.arr_double.arr =
           static_cast<double*>(std::malloc(size * sizeof(double)));
diff --git a/src/WireDecoder.h b/src/WireDecoder.h
index 43ecff1554..053ea90728 100644
--- a/src/WireDecoder.h
+++ b/src/WireDecoder.h
@@ -45,8 +45,9 @@ class WireDecoder {
   /* Reads the specified number of bytes.
    * @param buf pointer to read data (output parameter)
    * @param len number of bytes to read
+   * Caution: the buffer is only temporarily valid.
    */
-  bool Read(char** buf, std::size_t len) {
+  bool Read(const char** buf, std::size_t len) {
     if (len > m_allocated) Realloc(len);
     *buf = m_buf;
     return m_is.read(m_buf, len);
@@ -54,7 +55,7 @@ class WireDecoder {
 
   /* Reads a single byte. */
   bool Read8(unsigned int* val) {
-    char* buf;
+    const char* buf;
     if (!Read(&buf, 1)) return false;
     *val = (*((unsigned char*)buf)) & 0xff;
     return true;
@@ -62,7 +63,7 @@ class WireDecoder {
 
   /* Reads a 16-bit word. */
   bool Read16(unsigned int* val) {
-    char* buf;
+    const char* buf;
     if (!Read(&buf, 2)) return false;
     unsigned int v = (*((unsigned char*)buf)) & 0xff;
     ++buf;
@@ -74,7 +75,7 @@ class WireDecoder {
 
   /* Reads a 32-bit word. */
   bool Read32(unsigned long* val) {
-    char* buf;
+    const char* buf;
     if (!Read(&buf, 4)) return false;
     unsigned int v = (*((unsigned char*)buf)) & 0xff;
     ++buf;