diff --git a/applypatch/applypatch.c b/applypatch/applypatch.c
index 60e9e4a..bfb9440 100644
--- a/applypatch/applypatch.c
+++ b/applypatch/applypatch.c
@@ -32,7 +32,7 @@
 #include "edify/expr.h"
 
 static int LoadPartitionContents(const char* filename, FileContents* file);
-static ssize_t FileSink(unsigned char* data, ssize_t len, void* token);
+static ssize_t FileSink(const unsigned char* data, ssize_t len, void* token);
 static int GenerateTarget(FileContents* source_file,
                           const Value* source_patch_value,
                           FileContents* copy_file,
@@ -599,7 +599,7 @@
     return 0;
 }
 
-ssize_t FileSink(unsigned char* data, ssize_t len, void* token) {
+ssize_t FileSink(const unsigned char* data, ssize_t len, void* token) {
     int fd = *(int *)token;
     ssize_t done = 0;
     ssize_t wrote;
@@ -620,7 +620,7 @@
     ssize_t pos;
 } MemorySinkInfo;
 
-ssize_t MemorySink(unsigned char* data, ssize_t len, void* token) {
+ssize_t MemorySink(const unsigned char* data, ssize_t len, void* token) {
     MemorySinkInfo* msi = (MemorySinkInfo*)token;
     if (msi->size - msi->pos < len) {
         return -1;
diff --git a/applypatch/applypatch.h b/applypatch/applypatch.h
index ee54c24..edec848 100644
--- a/applypatch/applypatch.h
+++ b/applypatch/applypatch.h
@@ -40,7 +40,7 @@
 // and use it as the source instead.
 #define CACHE_TEMP_SOURCE "/cache/saved.file"
 
-typedef ssize_t (*SinkFn)(unsigned char*, ssize_t, void*);
+typedef ssize_t (*SinkFn)(const unsigned char*, ssize_t, void*);
 
 // applypatch.c
 int ShowLicenses();
diff --git a/applypatch/bspatch.c b/applypatch/bspatch.c
index 1dc7ab1..b34ec2a 100644
--- a/applypatch/bspatch.c
+++ b/applypatch/bspatch.c
@@ -112,9 +112,7 @@
         printf("short write of output: %d (%s)\n", errno, strerror(errno));
         return 1;
     }
-    if (ctx) {
-        SHA_update(ctx, new_data, new_size);
-    }
+    if (ctx) SHA_update(ctx, new_data, new_size);
     free(new_data);
 
     return 0;
diff --git a/applypatch/imgpatch.c b/applypatch/imgpatch.c
index af4d072..33c4487 100644
--- a/applypatch/imgpatch.c
+++ b/applypatch/imgpatch.c
@@ -95,7 +95,7 @@
                 printf("failed to read chunk %d raw data\n", i);
                 return -1;
             }
-            SHA_update(ctx, patch->data + pos, data_len);
+            if (ctx) SHA_update(ctx, patch->data + pos, data_len);
             if (sink((unsigned char*)patch->data + pos,
                      data_len, token) != data_len) {
                 printf("failed to write chunk %d raw data\n", i);
@@ -217,7 +217,7 @@
                            (long)have);
                     return -1;
                 }
-                SHA_update(ctx, temp_data, have);
+                if (ctx) SHA_update(ctx, temp_data, have);
             } while (ret != Z_STREAM_END);
             deflateEnd(&strm);