diff --git a/ChangeLog b/ChangeLog
index ae0abf27ec8be40862463c0fc6c505bb33425199..cf860feebe17a78e05781440cf8ba59b114cd751 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,10 @@
+2016-10-10  Niels Möller  <nisse@lysator.liu.se>
+
+	* write-be32.c (_nettle_write_be32): Use const for source argument.
+	* write-le32.c (_nettle_write_le32): Likewise.
+	* write-le64.c (_nettle_write_le64): Likewise.
+	* nettle-write.h: Update prototypes.
+
 2016-10-01  Niels Möller  <nisse@lysator.liu.se>
 
 	* Released nettle-3.3.
diff --git a/nettle-write.h b/nettle-write.h
index 75f4679b05f83164a8debd6ad6bd38a4ec064e37..6ca99632ea8bcc9a1060f1cce470edd276d03f0d 100644
--- a/nettle-write.h
+++ b/nettle-write.h
@@ -46,13 +46,13 @@
 /* FIXME: Use a macro shortcut to memcpy for native endianness. */
 void
 _nettle_write_be32(size_t length, uint8_t *dst,
-		   uint32_t *src);
+		   const uint32_t *src);
 void
 _nettle_write_le32(size_t length, uint8_t *dst,
-		   uint32_t *src);
+		   const uint32_t *src);
 
 void
 _nettle_write_le64(size_t length, uint8_t *dst,
-		   uint64_t *src);
+		   const uint64_t *src);
 
 #endif /* NETTLE_WRITE_H_INCLUDED */
diff --git a/write-be32.c b/write-be32.c
index a03ba59332b02b5e3543b0a295bb144b7ad4beb3..39d18627f5690ab2146e8021ce0eb758547f4d24 100644
--- a/write-be32.c
+++ b/write-be32.c
@@ -41,7 +41,7 @@
 
 void
 _nettle_write_be32(size_t length, uint8_t *dst,
-		   uint32_t *src)
+		   const uint32_t *src)
 {
   size_t i;
   size_t words;
diff --git a/write-le32.c b/write-le32.c
index 3635b66abcb20d5a7b681dfc2373aa71e7e99564..03816fbeb0c48c597538bef102d60d85b16dd8fe 100644
--- a/write-le32.c
+++ b/write-le32.c
@@ -41,7 +41,7 @@
 
 void
 _nettle_write_le32(size_t length, uint8_t *dst,
-		   uint32_t *src)
+		   const uint32_t *src)
 {
   size_t i;
   size_t words;
diff --git a/write-le64.c b/write-le64.c
index 4de42e799c2e803bf842800ad077dea8af287bcd..6623bbbeb6752981d884630a50e12e0d01a086f3 100644
--- a/write-le64.c
+++ b/write-le64.c
@@ -39,7 +39,7 @@
 
 void
 _nettle_write_le64(size_t length, uint8_t *dst,
-		   uint64_t *src)
+		   const uint64_t *src)
 {
   size_t i;
   size_t words;