diff --git a/util.c b/util.c
index 768410c318..575127421c 100644
--- a/util.c
+++ b/util.c
@@ -44,7 +44,7 @@ void data2hex(const void *data, uint32_t len, char *str)
 	str[len * 2] = 0;
 }
 
-uint32_t readprotobufint(uint8_t **ptr)
+uint32_t readprotobufint(const uint8_t **ptr)
 {
 	uint32_t result = (**ptr & 0x7F);
 	if (**ptr & 0x80) {
diff --git a/util.h b/util.h
index 03faf2dc8d..384ede0e32 100644
--- a/util.h
+++ b/util.h
@@ -42,7 +42,7 @@ void uint32hex(uint32_t num, char *str);
 void data2hex(const void *data, uint32_t len, char *str);
 
 // read protobuf integer and advance pointer
-uint32_t readprotobufint(uint8_t **ptr);
+uint32_t readprotobufint(const uint8_t **ptr);
 
 extern void __attribute__((noreturn)) shutdown(void);