diff --git a/src/bitmap.c b/src/bitmap.c
index 5b0d9cb..f4797cf 100644
--- a/src/bitmap.c
+++ b/src/bitmap.c
@@ -17,14 +17,14 @@
 #include "main.h"
 #include "bitmap.h"
 
-int bitmap_compare(bitmap_t *a, bitmap_t *b)
+int bitmap_compare(const unsigned char *a, const unsigned char *b)
 {
-  uint16_t row = 0;
-  uint16_t diff = 0;
-  size_t  cnt = 0;
+  unsigned char diff = 0;
+  size_t i = 0;
+  size_t cnt = 0;
 
-  for (row = 0; row < 16; row++) {
-    diff = (*a)[row] ^ (*b)[row];
+  for (i = 0; i < BITMAP_SIZE; i++, a++, b++) {
+    diff = *a ^ *b;
     while (diff) {
       cnt += (diff & 1);
       diff >>= 1;
diff --git a/src/bitmap.h b/src/bitmap.h
index 493c779..981b22b 100644
--- a/src/bitmap.h
+++ b/src/bitmap.h
@@ -1,6 +1,9 @@
 #ifndef HAS_BITMAP_H
-typedef uint16_t bitmap_t[16];
 
-int bitmap_compare(bitmap_t *a, bitmap_t *b);
+#define BITMAP_SIZE 32
+
+typedef unsigned char bitmap_t[BITMAP_SIZE];
+
+int bitmap_compare(const unsigned char *a, const unsigned char *b);
 #endif
-#define HAS_BITMAP_H
+#define HAS_BITMAP_H 1
diff --git a/tests/Makefile b/tests/Makefile
index 42a2f16..78ea1c4 100644
--- a/tests/Makefile
+++ b/tests/Makefile
@@ -8,3 +8,6 @@ CFLAGS=-Wall -Wextra -O0 -g -ggdb -pedantic
 SRC=../src/bitmap.c bitmap.c
 test-bitmap:
 	gcc $(CFLAGS) $(SRC) -o $@
+
+clean:
+	rm -f test-bitmap
diff --git a/tests/bitmap.c b/tests/bitmap.c
index 3021ed3..25a3b25 100644
--- a/tests/bitmap.c
+++ b/tests/bitmap.c
@@ -4,31 +4,31 @@
 int
 main(int argc, char **argv)
 {
-  bitmap a, b;
+  bitmap_t a, b;
 
-  memset (&a, 0x00, 16 * sizeof(uint16_t));
-  memset (&b, 0x00, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 0);
+  memset (a, 0x00, sizeof(bitmap_t));
+  memset (b, 0x00, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 0);
 
-  memset (&a, 0xFE, 16 * sizeof(uint16_t));
-  memset (&b, 0xFF, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 32);
+  memset (a, 0xFE, sizeof(bitmap_t));
+  memset (b, 0xFF, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 32);
 
-  memset (&a, 0x00, 16 * sizeof(uint16_t));
-  memset (&b, 0x55, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 128);
+  memset (a, 0x00, sizeof(bitmap_t));
+  memset (b, 0x55, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 128);
 
-  memset (&a, 0x00, 16 * sizeof(uint16_t));
-  memset (&b, 0xAA, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 128);
+  memset (a, 0x00, sizeof(bitmap_t));
+  memset (b, 0xAA, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 128);
 
-  memset (&a, 0xAA, 16 * sizeof(uint16_t));
-  memset (&b, 0x55, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 256);
+  memset (a, 0xAA, sizeof(bitmap_t));
+  memset (b, 0x55, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 256);
 
-  memset (&a, 0x00, 16 * sizeof(uint16_t));
-  memset (&b, 0xFF, 16 * sizeof(uint16_t));
-  assert(bitmap_compare(&a, &b) == 256);
+  memset (a, 0x00, sizeof(bitmap_t));
+  memset (b, 0xFF, sizeof(bitmap_t));
+  assert(bitmap_compare(a, b) == 256);
 
   return 0;
 }