diff --git a/applypatch/Android.mk b/applypatch/Android.mk
index ec3c6ee..3c88d1f 100644
--- a/applypatch/Android.mk
+++ b/applypatch/Android.mk
@@ -35,7 +35,9 @@
     libcrypto \
     libbz \
     libz
-LOCAL_CFLAGS := -Werror
+LOCAL_CFLAGS := \
+    -DZLIB_CONST \
+    -Werror
 include $(BUILD_STATIC_LIBRARY)
 
 # libimgpatch (static library)
@@ -54,7 +56,9 @@
     libcrypto \
     libbz \
     libz
-LOCAL_CFLAGS := -Werror
+LOCAL_CFLAGS := \
+    -DZLIB_CONST \
+    -Werror
 include $(BUILD_STATIC_LIBRARY)
 
 # libimgpatch (host static library)
@@ -74,7 +78,9 @@
     libcrypto \
     libbz \
     libz
-LOCAL_CFLAGS := -Werror
+LOCAL_CFLAGS := \
+    -DZLIB_CONST \
+    -Werror
 include $(BUILD_HOST_STATIC_LIBRARY)
 
 # libapplypatch_modes (static library)
diff --git a/applypatch/imgpatch.cpp b/applypatch/imgpatch.cpp
index ae6071f..00ea90e 100644
--- a/applypatch/imgpatch.cpp
+++ b/applypatch/imgpatch.cpp
@@ -160,7 +160,7 @@
         strm.zfree = Z_NULL;
         strm.opaque = Z_NULL;
         strm.avail_in = src_len;
-        strm.next_in = const_cast<unsigned char*>(old_data + src_start);
+        strm.next_in = old_data + src_start;
         strm.avail_out = expanded_len;
         strm.next_out = expanded_source.data();