diff --git a/crc10.c b/crc10.c
index 2ddddcb..025018d 100644
--- a/crc10.c
+++ b/crc10.c
@@ -1,3 +1,5 @@
+#include <stdbool.h>
+
 static unsigned short table[256] =
 {
     0x0000, 0x048f, 0x091e, 0x0d91, 0x123c, 0x16b3, 0x1b22, 0x1fad,
@@ -51,7 +53,7 @@ short crc10(unsigned char const *data, int length)
     return remainder & 0x03ff;
 }
 
-short crc10_check(unsigned char const *data, int length)
+bool crc10_check(unsigned char const *data, int length)
 {
     return !crc10(data, length);
 }
diff --git a/crc12.c b/crc12.c
index f666edf..a4dc144 100644
--- a/crc12.c
+++ b/crc12.c
@@ -1,3 +1,5 @@
+#include <stdbool.h>
+
 static unsigned short table[256] =
 {
     0x0000, 0x1c06, 0x340a, 0x280c, 0x6814, 0x7412, 0x5c1e, 0x4018,
@@ -51,7 +53,7 @@ short crc12(unsigned char const *data, int length)
     return remainder & 0x0fff;
 }
 
-short crc12_check(unsigned char const *data, int length)
+bool crc12_check(unsigned char const *data, int length)
 {
     return !crc12(data, length);
 }