diff --git a/src/runtime/c/pgf/md5.cxx b/src/runtime/c/pgf/md5.cxx
index 6a8b4c8cb..a905788e4 100644
--- a/src/runtime/c/pgf/md5.cxx
+++ b/src/runtime/c/pgf/md5.cxx
@@ -129,7 +129,7 @@ void md5Step(uint32_t *buffer, uint32_t *input){
  * If the input fills out a block of 512 bits, apply the algorithm (md5Step)
  * and save the result in the buffer. Also updates the overall size.
  */
-void MD5Context::update(uint8_t *input_buffer, size_t input_len)
+void MD5Context::update(const uint8_t *input_buffer, size_t input_len)
 {
     uint32_t input[16];
     unsigned int offset = this->size % 64;
diff --git a/src/runtime/c/pgf/md5.h b/src/runtime/c/pgf/md5.h
index 1e33226ec..65fe20170 100644
--- a/src/runtime/c/pgf/md5.h
+++ b/src/runtime/c/pgf/md5.h
@@ -16,12 +16,12 @@ class PGF_INTERNAL_DECL MD5Context {
 
 public:
     MD5Context();
-    void update(uint8_t *input, size_t input_len);
+    void update(const uint8_t *input, size_t input_len);
 
     template <class T>
-    void update(T &input)
+    void update(const T &input)
     {
-        update((uint8_t *) &input, sizeof(T));
+        update((const uint8_t *) &input, sizeof(T));
     }
 
     void finalize(MD5Digest *digest);