diff --git a/tests/test_block_header.c b/tests/test_block_header.c
index c6767e38..b50198ce 100644
--- a/tests/test_block_header.c
+++ b/tests/test_block_header.c
@@ -337,7 +337,7 @@ test4(void)
 
 
 int
-main()
+main(void)
 {
 	lzma_init();
 
diff --git a/tests/test_check.c b/tests/test_check.c
index 14df375a..cb6b8ec1 100644
--- a/tests/test_check.c
+++ b/tests/test_check.c
@@ -79,7 +79,7 @@ test_crc64(void)
 
 
 int
-main()
+main(void)
 {
 	bool error = false;
 
diff --git a/tests/test_filter_flags.c b/tests/test_filter_flags.c
index 0a16f21a..bab344ae 100644
--- a/tests/test_filter_flags.c
+++ b/tests/test_filter_flags.c
@@ -310,7 +310,7 @@ test_lzma(void)
 
 
 int
-main()
+main(void)
 {
 	lzma_init();
 
diff --git a/tests/test_index.c b/tests/test_index.c
index 399963d3..2c006045 100644
--- a/tests/test_index.c
+++ b/tests/test_index.c
@@ -21,21 +21,21 @@
 
 
 int
-main()
+main(void)
 {
-	lzma_index index[3] = {
-		{ 22, 33, index + 1 },
-		{ 44, 55, index + 2 },
+	lzma_index my_index[3] = {
+		{ 22, 33, my_index + 1 },
+		{ 44, 55, my_index + 2 },
 		{ 66, 77, NULL },
 	};
 
-	lzma_index *i = lzma_index_dup(index, NULL);
+	lzma_index *i = lzma_index_dup(my_index, NULL);
 	expect(i != NULL);
 
-	expect(lzma_index_is_equal(index, i));
+	expect(lzma_index_is_equal(my_index, i));
 
 	i->next->next->uncompressed_size = 99;
-	expect(!lzma_index_is_equal(index, i));
+	expect(!lzma_index_is_equal(my_index, i));
 
 	lzma_index_free(i, NULL);
 
diff --git a/tests/test_info.c b/tests/test_info.c
index e7899ef3..c073fafe 100644
--- a/tests/test_info.c
+++ b/tests/test_info.c
@@ -693,7 +693,7 @@ test9(void)
 
 
 int
-main()
+main(void)
 {
 	lzma_init();
 
diff --git a/tests/test_stream_flags.c b/tests/test_stream_flags.c
index 4cd22576..99e55d5e 100644
--- a/tests/test_stream_flags.c
+++ b/tests/test_stream_flags.c
@@ -162,7 +162,7 @@ test_decode_invalid(void)
 
 
 int
-main()
+main(void)
 {
 	lzma_init();