diff --git a/Android.mk b/Android.mk
index 1de97361e..69859278f 100644
--- a/Android.mk
+++ b/Android.mk
@@ -154,6 +154,7 @@ LOCAL_SHARED_LIBRARIES := libcutils
 
 LOCAL_CFLAGS                                             += \
     -DOPENTHREAD_ENABLE_ANDROID_NDK=1                       \
+    -Wno-sign-compare                                       \
     $(NULL)
 endif
 
@@ -473,6 +474,18 @@ LOCAL_SRC_FILES                                                  := \
     third_party/mbedtls/repo/library/x509write_crt.c                \
     third_party/mbedtls/repo/library/x509write_csr.c                \
     third_party/mbedtls/repo/library/xtea.c                         \
+    third_party/tcplp/bsdtcp/tcp_usrreq.c                           \
+    third_party/tcplp/bsdtcp/tcp_subr.c                             \
+    third_party/tcplp/bsdtcp/tcp_output.c                           \
+    third_party/tcplp/bsdtcp/cc/cc_newreno.c                        \
+    third_party/tcplp/bsdtcp/tcp_reass.c                            \
+    third_party/tcplp/bsdtcp/tcp_timewait.c                         \
+    third_party/tcplp/bsdtcp/tcp_sack.c                             \
+    third_party/tcplp/bsdtcp/tcp_input.c                            \
+    third_party/tcplp/bsdtcp/tcp_timer.c                            \
+    third_party/tcplp/lib/bitmap.c                                  \
+    third_party/tcplp/lib/cbuf.c                                    \
+    third_party/tcplp/lib/lbuf.c                                    \
     $(OPENTHREAD_PROJECT_SRC_FILES)                                 \
     $(NULL)
 
diff --git a/third_party/tcplp/bsdtcp/tcp_output.c b/third_party/tcplp/bsdtcp/tcp_output.c
index 104403f51..695257b79 100644
--- a/third_party/tcplp/bsdtcp/tcp_output.c
+++ b/third_party/tcplp/bsdtcp/tcp_output.c
@@ -895,10 +895,11 @@ send:
 			size_t start_offset;
 			otLinkedBuffer* end;
 			size_t end_offset;
+			otLinkedBuffer* curr;
 			int rv = lbuf_getrange(&tp->sendbuf, off, len, &start, &start_offset, &end, &end_offset);
-			KASSERT(rv == 0, ("Reading send buffer out of range!\n"));
 			size_t message_offset = otMessageGetOffset(message) + sizeof(struct tcphdr) + optlen;
-			for (otLinkedBuffer* curr = start; curr != end->mNext; curr = curr->mNext) {
+			KASSERT(rv == 0, ("Reading send buffer out of range!\n"));
+			for (curr = start; curr != end->mNext; curr = curr->mNext) {
 				const uint8_t* data_to_copy = curr->mData;
 				size_t length_to_copy = curr->mLength;
 				if (curr == start) {