diff --git a/ChangeLog b/ChangeLog
index aeb55b56ae5d9ff71e0c2db460beaef0f87c1577..3d12926c2035d1e10efc8b37efdb2657b92ec8d9 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,5 +1,10 @@
 2015-03-12  Niels Möller  <nisse@diamant.hack.org>
 
+	* base64.h (struct base64_encode_ctx): Micro optimization of
+	struct layout, saving a few bytes.
+	(struct base64_decode_ctx): Likewise.
+	* base16.h (struct base16_decode_ctx): Likewise.
+
 	* nettle.texinfo (ASCII encoding): Document base64url functions.
 
 2015-03-10  Niels Möller  <nisse@diamant.hack.org>
diff --git a/base16.h b/base16.h
index 3facfd4edd83ffc9ad724b890308e83c01cbbb50..2579c0efa661a24d758559a6bd0601cbda660948 100644
--- a/base16.h
+++ b/base16.h
@@ -74,8 +74,8 @@ base16_encode_update(uint8_t *dst,
 
 struct base16_decode_ctx
 {
-  unsigned word;   /* Leftover bits */
-  unsigned bits;   /* Number buffered bits */
+  unsigned char word; /* Leftover bits */
+  unsigned char bits; /* Number buffered bits */
 };
 
 void
diff --git a/base64.h b/base64.h
index 10c4965c49016d7658192b70d28e166586c0ed4e..79194bd4f6ed5b818984f50a29e24342d6191b6f 100644
--- a/base64.h
+++ b/base64.h
@@ -73,9 +73,9 @@ extern "C" {
 
 struct base64_encode_ctx
 {
-  unsigned word;   /* Leftover bits */
-  unsigned bits;  /* Number of bits, always 0, 2, or 4. */
   const uint8_t *alphabet; /* Alphabet to use for encoding */
+  unsigned short word;     /* Leftover bits */
+  unsigned char bits;      /* Number of bits, always 0, 2, or 4. */
 };
 
 /* Initialize encoding context for base-64 */
@@ -126,12 +126,12 @@ base64_encode_group(uint8_t *dst, uint32_t group);
 
 struct base64_decode_ctx
 {
-  unsigned word;   /* Leftover bits */
-  unsigned bits;   /* Number buffered bits */
+  const signed char *table; /* Decoding table */
+  unsigned short word;      /* Leftover bits */
+  unsigned char bits;       /* Number buffered bits */
 
   /* Number of padding characters encountered */
-  unsigned padding;
-  const signed char *table; /* Decoding table */
+  unsigned char padding;
 };
 
 /* Initialize decoding context for base-64 */