diff --git a/include/polarssl/aes.h b/include/polarssl/aes.h
index 11db17c..5e18ab7 100644
--- a/include/polarssl/aes.h
+++ b/include/polarssl/aes.h
@@ -26,7 +26,7 @@
 #define AES_ENCRYPT     1
 #define AES_DECRYPT     0
 
-#define POLARSSL_ERR_AES_INVALID_KEY_LENGTH                 0x0800
+#define POLARSSL_ERR_AES_INVALID_KEY_LENGTH                 -0x0800
 
 /**
  * \brief          AES context structure
diff --git a/include/polarssl/camellia.h b/include/polarssl/camellia.h
index efdc11b..2037e73 100644
--- a/include/polarssl/camellia.h
+++ b/include/polarssl/camellia.h
@@ -31,7 +31,7 @@
 #define CAMELLIA_ENCRYPT     1
 #define CAMELLIA_DECRYPT     0
 
-#define POLARSSL_ERR_CAMELLIA_INVALID_KEY_LENGTH            0x0a00
+#define POLARSSL_ERR_CAMELLIA_INVALID_KEY_LENGTH            -0x0a00
 
 /**
  * \brief          CAMELLIA context structure
diff --git a/include/polarssl/net.h b/include/polarssl/net.h
index 29d6661..eff53cb 100644
--- a/include/polarssl/net.h
+++ b/include/polarssl/net.h
@@ -23,16 +23,16 @@
 #ifndef POLARSSL_NET_H
 #define POLARSSL_NET_H
 
-#define POLARSSL_ERR_NET_UNKNOWN_HOST                      0x0F00
-#define POLARSSL_ERR_NET_SOCKET_FAILED                     0x0F10
-#define POLARSSL_ERR_NET_CONNECT_FAILED                    0x0F20
-#define POLARSSL_ERR_NET_BIND_FAILED                       0x0F30
-#define POLARSSL_ERR_NET_LISTEN_FAILED                     0x0F40
-#define POLARSSL_ERR_NET_ACCEPT_FAILED                     0x0F50
-#define POLARSSL_ERR_NET_RECV_FAILED                       0x0F60
-#define POLARSSL_ERR_NET_SEND_FAILED                       0x0F70
-#define POLARSSL_ERR_NET_CONN_RESET                        0x0F80
-#define POLARSSL_ERR_NET_TRY_AGAIN                         0x0F90
+#define POLARSSL_ERR_NET_UNKNOWN_HOST                      -0x0F00
+#define POLARSSL_ERR_NET_SOCKET_FAILED                     -0x0F10
+#define POLARSSL_ERR_NET_CONNECT_FAILED                    -0x0F20
+#define POLARSSL_ERR_NET_BIND_FAILED                       -0x0F30
+#define POLARSSL_ERR_NET_LISTEN_FAILED                     -0x0F40
+#define POLARSSL_ERR_NET_ACCEPT_FAILED                     -0x0F50
+#define POLARSSL_ERR_NET_RECV_FAILED                       -0x0F60
+#define POLARSSL_ERR_NET_SEND_FAILED                       -0x0F70
+#define POLARSSL_ERR_NET_CONN_RESET                        -0x0F80
+#define POLARSSL_ERR_NET_TRY_AGAIN                         -0x0F90
 
 #ifdef __cplusplus
 extern "C" {
diff --git a/include/polarssl/rsa.h b/include/polarssl/rsa.h
index 26dddbc..295a2db 100644
--- a/include/polarssl/rsa.h
+++ b/include/polarssl/rsa.h
@@ -28,14 +28,14 @@
 /*
  * RSA Error codes
  */
-#define POLARSSL_ERR_RSA_BAD_INPUT_DATA                    0x0400
-#define POLARSSL_ERR_RSA_INVALID_PADDING                   0x0410
-#define POLARSSL_ERR_RSA_KEY_GEN_FAILED                    0x0420
-#define POLARSSL_ERR_RSA_KEY_CHECK_FAILED                  0x0430
-#define POLARSSL_ERR_RSA_PUBLIC_FAILED                     0x0440
-#define POLARSSL_ERR_RSA_PRIVATE_FAILED                    0x0450
-#define POLARSSL_ERR_RSA_VERIFY_FAILED                     0x0460
-#define POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE                  0x0470
+#define POLARSSL_ERR_RSA_BAD_INPUT_DATA                    -0x0400
+#define POLARSSL_ERR_RSA_INVALID_PADDING                   -0x0410
+#define POLARSSL_ERR_RSA_KEY_GEN_FAILED                    -0x0420
+#define POLARSSL_ERR_RSA_KEY_CHECK_FAILED                  -0x0430
+#define POLARSSL_ERR_RSA_PUBLIC_FAILED                     -0x0440
+#define POLARSSL_ERR_RSA_PRIVATE_FAILED                    -0x0450
+#define POLARSSL_ERR_RSA_VERIFY_FAILED                     -0x0460
+#define POLARSSL_ERR_RSA_OUTPUT_TOO_LARGE                  -0x0470
 
 /*
  * PKCS#1 constants
diff --git a/include/polarssl/ssl.h b/include/polarssl/ssl.h
index fa75557..3868505 100644
--- a/include/polarssl/ssl.h
+++ b/include/polarssl/ssl.h
@@ -35,33 +35,33 @@
 /*
  * SSL Error codes
  */
-#define POLARSSL_ERR_SSL_FEATURE_UNAVAILABLE               0x1000
-#define POLARSSL_ERR_SSL_BAD_INPUT_DATA                    0x1800
-#define POLARSSL_ERR_SSL_INVALID_MAC                       0x2000
-#define POLARSSL_ERR_SSL_INVALID_RECORD                    0x2800
-#define POLARSSL_ERR_SSL_INVALID_MODULUS_SIZE              0x3000
-#define POLARSSL_ERR_SSL_UNKNOWN_CIPHER                    0x3800
-#define POLARSSL_ERR_SSL_NO_CIPHER_CHOSEN                  0x4000
-#define POLARSSL_ERR_SSL_NO_SESSION_FOUND                  0x4800
-#define POLARSSL_ERR_SSL_NO_CLIENT_CERTIFICATE             0x5000
-#define POLARSSL_ERR_SSL_CERTIFICATE_TOO_LARGE             0x5800
-#define POLARSSL_ERR_SSL_CERTIFICATE_REQUIRED              0x6000
-#define POLARSSL_ERR_SSL_PRIVATE_KEY_REQUIRED              0x6800
-#define POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED                 0x7000
-#define POLARSSL_ERR_SSL_UNEXPECTED_MESSAGE                0x7800
-#define POLARSSL_ERR_SSL_FATAL_ALERT_MESSAGE               0x8000
-#define POLARSSL_ERR_SSL_PEER_VERIFY_FAILED                0x8800
-#define POLARSSL_ERR_SSL_PEER_CLOSE_NOTIFY                 0x9000
-#define POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO               0x9800
-#define POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO               0xA000
-#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE                0xA800
-#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST        0xB000
-#define POLARSSL_ERR_SSL_BAD_HS_SERVER_KEY_EXCHANGE        0xB800
-#define POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO_DONE          0xC000
-#define POLARSSL_ERR_SSL_BAD_HS_CLIENT_KEY_EXCHANGE        0xC800
-#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE_VERIFY         0xD000
-#define POLARSSL_ERR_SSL_BAD_HS_CHANGE_CIPHER_SPEC         0xD800
-#define POLARSSL_ERR_SSL_BAD_HS_FINISHED                   0xE000
+#define POLARSSL_ERR_SSL_FEATURE_UNAVAILABLE               -0x1000
+#define POLARSSL_ERR_SSL_BAD_INPUT_DATA                    -0x1800
+#define POLARSSL_ERR_SSL_INVALID_MAC                       -0x2000
+#define POLARSSL_ERR_SSL_INVALID_RECORD                    -0x2800
+#define POLARSSL_ERR_SSL_INVALID_MODULUS_SIZE              -0x3000
+#define POLARSSL_ERR_SSL_UNKNOWN_CIPHER                    -0x3800
+#define POLARSSL_ERR_SSL_NO_CIPHER_CHOSEN                  -0x4000
+#define POLARSSL_ERR_SSL_NO_SESSION_FOUND                  -0x4800
+#define POLARSSL_ERR_SSL_NO_CLIENT_CERTIFICATE             -0x5000
+#define POLARSSL_ERR_SSL_CERTIFICATE_TOO_LARGE             -0x5800
+#define POLARSSL_ERR_SSL_CERTIFICATE_REQUIRED              -0x6000
+#define POLARSSL_ERR_SSL_PRIVATE_KEY_REQUIRED              -0x6800
+#define POLARSSL_ERR_SSL_CA_CHAIN_REQUIRED                 -0x7000
+#define POLARSSL_ERR_SSL_UNEXPECTED_MESSAGE                -0x7800
+#define POLARSSL_ERR_SSL_FATAL_ALERT_MESSAGE               -0x8000
+#define POLARSSL_ERR_SSL_PEER_VERIFY_FAILED                -0x8800
+#define POLARSSL_ERR_SSL_PEER_CLOSE_NOTIFY                 -0x9000
+#define POLARSSL_ERR_SSL_BAD_HS_CLIENT_HELLO               -0x9800
+#define POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO               -0xA000
+#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE                -0xA800
+#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE_REQUEST        -0xB000
+#define POLARSSL_ERR_SSL_BAD_HS_SERVER_KEY_EXCHANGE        -0xB800
+#define POLARSSL_ERR_SSL_BAD_HS_SERVER_HELLO_DONE          -0xC000
+#define POLARSSL_ERR_SSL_BAD_HS_CLIENT_KEY_EXCHANGE        -0xC800
+#define POLARSSL_ERR_SSL_BAD_HS_CERTIFICATE_VERIFY         -0xD000
+#define POLARSSL_ERR_SSL_BAD_HS_CHANGE_CIPHER_SPEC         -0xD800
+#define POLARSSL_ERR_SSL_BAD_HS_FINISHED                   -0xE000
 
 /*
  * Various constants
diff --git a/include/polarssl/x509.h b/include/polarssl/x509.h
index a218e8a..fbb1b67 100644
--- a/include/polarssl/x509.h
+++ b/include/polarssl/x509.h
@@ -40,31 +40,31 @@
 /*
  * X509 Error codes
  */
-#define POLARSSL_ERR_X509_FEATURE_UNAVAILABLE              0x0020
-#define POLARSSL_ERR_X509_CERT_INVALID_PEM                 0x0040
-#define POLARSSL_ERR_X509_CERT_INVALID_FORMAT              0x0060
-#define POLARSSL_ERR_X509_CERT_INVALID_VERSION             0x0080
-#define POLARSSL_ERR_X509_CERT_INVALID_SERIAL              0x00A0
-#define POLARSSL_ERR_X509_CERT_INVALID_ALG                 0x00C0
-#define POLARSSL_ERR_X509_CERT_INVALID_NAME                0x00E0
-#define POLARSSL_ERR_X509_CERT_INVALID_DATE                0x0100
-#define POLARSSL_ERR_X509_CERT_INVALID_PUBKEY              0x0120
-#define POLARSSL_ERR_X509_CERT_INVALID_SIGNATURE           0x0140
-#define POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS          0x0160
-#define POLARSSL_ERR_X509_CERT_UNKNOWN_VERSION             0x0180
-#define POLARSSL_ERR_X509_CERT_UNKNOWN_SIG_ALG             0x01A0
-#define POLARSSL_ERR_X509_CERT_UNKNOWN_PK_ALG              0x01C0
-#define POLARSSL_ERR_X509_CERT_SIG_MISMATCH                0x01E0
-#define POLARSSL_ERR_X509_CERT_VERIFY_FAILED               0x0200
-#define POLARSSL_ERR_X509_KEY_INVALID_PEM                  0x0220
-#define POLARSSL_ERR_X509_KEY_INVALID_VERSION              0x0240
-#define POLARSSL_ERR_X509_KEY_INVALID_FORMAT               0x0260
-#define POLARSSL_ERR_X509_KEY_INVALID_ENC_IV               0x0280
-#define POLARSSL_ERR_X509_KEY_UNKNOWN_ENC_ALG              0x02A0
-#define POLARSSL_ERR_X509_KEY_PASSWORD_REQUIRED            0x02C0
-#define POLARSSL_ERR_X509_KEY_PASSWORD_MISMATCH            0x02E0
-#define POLARSSL_ERR_X509_POINT_ERROR                      0x0300
-#define POLARSSL_ERR_X509_VALUE_TO_LENGTH                  0x0320
+#define POLARSSL_ERR_X509_FEATURE_UNAVAILABLE              -0x0020
+#define POLARSSL_ERR_X509_CERT_INVALID_PEM                 -0x0040
+#define POLARSSL_ERR_X509_CERT_INVALID_FORMAT              -0x0060
+#define POLARSSL_ERR_X509_CERT_INVALID_VERSION             -0x0080
+#define POLARSSL_ERR_X509_CERT_INVALID_SERIAL              -0x00A0
+#define POLARSSL_ERR_X509_CERT_INVALID_ALG                 -0x00C0
+#define POLARSSL_ERR_X509_CERT_INVALID_NAME                -0x00E0
+#define POLARSSL_ERR_X509_CERT_INVALID_DATE                -0x0100
+#define POLARSSL_ERR_X509_CERT_INVALID_PUBKEY              -0x0120
+#define POLARSSL_ERR_X509_CERT_INVALID_SIGNATURE           -0x0140
+#define POLARSSL_ERR_X509_CERT_INVALID_EXTENSIONS          -0x0160
+#define POLARSSL_ERR_X509_CERT_UNKNOWN_VERSION             -0x0180
+#define POLARSSL_ERR_X509_CERT_UNKNOWN_SIG_ALG             -0x01A0
+#define POLARSSL_ERR_X509_CERT_UNKNOWN_PK_ALG              -0x01C0
+#define POLARSSL_ERR_X509_CERT_SIG_MISMATCH                -0x01E0
+#define POLARSSL_ERR_X509_CERT_VERIFY_FAILED               -0x0200
+#define POLARSSL_ERR_X509_KEY_INVALID_PEM                  -0x0220
+#define POLARSSL_ERR_X509_KEY_INVALID_VERSION              -0x0240
+#define POLARSSL_ERR_X509_KEY_INVALID_FORMAT               -0x0260
+#define POLARSSL_ERR_X509_KEY_INVALID_ENC_IV               -0x0280
+#define POLARSSL_ERR_X509_KEY_UNKNOWN_ENC_ALG              -0x02A0
+#define POLARSSL_ERR_X509_KEY_PASSWORD_REQUIRED            -0x02C0
+#define POLARSSL_ERR_X509_KEY_PASSWORD_MISMATCH            -0x02E0
+#define POLARSSL_ERR_X509_POINT_ERROR                      -0x0300
+#define POLARSSL_ERR_X509_VALUE_TO_LENGTH                  -0x0320
 
 /*
  * X509 Verify codes