diff --git a/library/poly1305.c b/library/poly1305.c
index 542a850..0aa4533 100644
--- a/library/poly1305.c
+++ b/library/poly1305.c
@@ -259,7 +259,7 @@
 int mbedtls_poly1305_starts( mbedtls_poly1305_context *ctx,
                              const unsigned char key[32] )
 {
-    if ( ctx == NULL )
+    if ( ctx == NULL || key == NULL )
     {
         return( MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
     }
@@ -417,7 +417,7 @@
 
 cleanup:
     mbedtls_poly1305_free( &ctx );
-    return( 0 );
+    return( result );
 }
 
 #endif /* MBEDTLS_POLY1305_ALT */
diff --git a/tests/suites/test_suite_poly1305.data b/tests/suites/test_suite_poly1305.data
index f259e84..13912e9 100644
--- a/tests/suites/test_suite_poly1305.data
+++ b/tests/suites/test_suite_poly1305.data
@@ -1,51 +1,42 @@
 Poly1305 RFC 7539 Example And Test Vector
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"85d6be7857556d337f4452fe42d506a80103808afb0db2fd4abff6af4149f51b":"a8061dc1305136c6c22b8baf0c0127a9":"43727970746f6772617068696320466f72756d2052657365617263682047726f7570"
 
 Poly1305 RFC 7539 Test Vector #1
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0000000000000000000000000000000000000000000000000000000000000000":"00000000000000000000000000000000":"00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000"
 
 Poly1305 RFC 7539 Test Vector #2
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0000000000000000000000000000000036e5f6b5c5e06070f0efca96227a863e":"36e5f6b5c5e06070f0efca96227a863e":"416e79207375626d697373696f6e20746f20746865204945544620696e74656e6465642062792074686520436f6e7472696275746f7220666f72207075626c69636174696f6e20617320616c6c206f722070617274206f6620616e204945544620496e7465726e65742d4472616674206f722052464320616e6420616e792073746174656d656e74206d6164652077697468696e2074686520636f6e74657874206f6620616e204945544620616374697669747920697320636f6e7369646572656420616e20224945544620436f6e747269627574696f6e222e20537563682073746174656d656e747320696e636c756465206f72616c2073746174656d656e747320696e20494554462073657373696f6e732c2061732077656c6c206173207772697474656e20616e6420656c656374726f6e696320636f6d6d756e69636174696f6e73206d61646520617420616e792074696d65206f7220706c6163652c207768696368206172652061646472657373656420746f"
 
 Poly1305 RFC 7539 Test Vector #3
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"36e5f6b5c5e06070f0efca96227a863e00000000000000000000000000000000":"f3477e7cd95417af89a6b8794c310cf0":"416e79207375626d697373696f6e20746f20746865204945544620696e74656e6465642062792074686520436f6e7472696275746f7220666f72207075626c69636174696f6e20617320616c6c206f722070617274206f6620616e204945544620496e7465726e65742d4472616674206f722052464320616e6420616e792073746174656d656e74206d6164652077697468696e2074686520636f6e74657874206f6620616e204945544620616374697669747920697320636f6e7369646572656420616e20224945544620436f6e747269627574696f6e222e20537563682073746174656d656e747320696e636c756465206f72616c2073746174656d656e747320696e20494554462073657373696f6e732c2061732077656c6c206173207772697474656e20616e6420656c656374726f6e696320636f6d6d756e69636174696f6e73206d61646520617420616e792074696d65206f7220706c6163652c207768696368206172652061646472657373656420746f"
 
 Poly1305 RFC 7539 Test Vector #4
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"1c9240a5eb55d38af333888604f6b5f0473917c1402b80099dca5cbc207075c0":"4541669a7eaaee61e708dc7cbcc5eb62":"2754776173206272696c6c69672c20616e642074686520736c6974687920746f7665730a446964206779726520616e642067696d626c6520696e2074686520776162653a0a416c6c206d696d737920776572652074686520626f726f676f7665732c0a416e6420746865206d6f6d65207261746873206f757467726162652e"
 
 Poly1305 RFC 7539 Test Vector #5
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0200000000000000000000000000000000000000000000000000000000000000":"03000000000000000000000000000000":"ffffffffffffffffffffffffffffffff"
 
 Poly1305 RFC 7539 Test Vector #6
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"02000000000000000000000000000000ffffffffffffffffffffffffffffffff":"03000000000000000000000000000000":"02000000000000000000000000000000"
 
 Poly1305 RFC 7539 Test Vector #7
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0100000000000000000000000000000000000000000000000000000000000000":"05000000000000000000000000000000":"fffffffffffffffffffffffffffffffff0ffffffffffffffffffffffffffffff11000000000000000000000000000000"
 
 Poly1305 RFC 7539 Test Vector #8
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0100000000000000000000000000000000000000000000000000000000000000":"00000000000000000000000000000000":"fffffffffffffffffffffffffffffffffbfefefefefefefefefefefefefefefe01010101010101010101010101010101"
 
 Poly1305 RFC 7539 Test Vector #9
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0200000000000000000000000000000000000000000000000000000000000000":"faffffffffffffffffffffffffffffff":"fdffffffffffffffffffffffffffffff"
 
 Poly1305 RFC 7539 Test Vector #10
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0100000000000000040000000000000000000000000000000000000000000000":"14000000000000005500000000000000":"e33594d7505e43b900000000000000003394d7505e4379cd01000000000000000000000000000000000000000000000001000000000000000000000000000000"
 
 Poly1305 RFC 7539 Test Vector #11
-depends_on:MBEDTLS_POLY1305_C
 mbedtls_poly1305:"0100000000000000040000000000000000000000000000000000000000000000":"13000000000000000000000000000000":"e33594d7505e43b900000000000000003394d7505e4379cd010000000000000000000000000000000000000000000000"
 
+Poly1305 Parameter validation
+poly1305_bad_params:
+
 Poly1305 Selftest
-depends_on:MBEDTLS_SELF_TEST:MBEDTLS_POLY1305_C
+depends_on:MBEDTLS_SELF_TEST
 poly1305_selftest:
diff --git a/tests/suites/test_suite_poly1305.function b/tests/suites/test_suite_poly1305.function
index 682eb05..c5e7989 100644
--- a/tests/suites/test_suite_poly1305.function
+++ b/tests/suites/test_suite_poly1305.function
@@ -3,7 +3,12 @@
 #include <stddef.h>
 /* END_HEADER */
 
-/* BEGIN_CASE depends_on:MBEDTLS_POLY1305_C */
+/* BEGIN_DEPENDENCIES
+ * depends_on:MBEDTLS_POLY1305_C
+ * END_DEPENDENCIES
+ */
+
+/* BEGIN_CASE */
 void mbedtls_poly1305( char *hex_key_string, char *hex_mac_string, char *hex_src_string  )
 {
     unsigned char src_str[375]; /* max size of binary input */
@@ -24,7 +29,7 @@
     /*
      * Test the integrated API
      */
-    mbedtls_poly1305_mac( key, src_str, src_len, mac );
+    TEST_ASSERT( mbedtls_poly1305_mac( key, src_str, src_len, mac ) == 0 );
 
     hexify( mac_str, mac, 16 );
     TEST_ASSERT( strcmp( (char *) mac_str, hex_mac_string ) == 0 );
@@ -63,7 +68,51 @@
 }
 /* END_CASE */
 
-/* BEGIN_CASE depends_on:MBEDTLS_POLY1305_C:MBEDTLS_SELF_TEST */
+/* BEGIN_CASE */
+void poly1305_bad_params()
+{
+    unsigned char src[1];
+    unsigned char key[32];
+    unsigned char mac[16];
+    size_t src_len = sizeof( src );
+    mbedtls_poly1305_context ctx;
+
+    mbedtls_poly1305_init( NULL );
+    mbedtls_poly1305_free( NULL );
+
+    mbedtls_poly1305_init( &ctx );
+
+    TEST_ASSERT( mbedtls_poly1305_starts( NULL, key )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_starts( &ctx, NULL )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_poly1305_update( NULL, src, 0 )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_update( &ctx, NULL, src_len )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_update( &ctx, NULL, 0 )
+                 == 0 );
+
+    TEST_ASSERT( mbedtls_poly1305_finish( NULL, mac )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_finish( &ctx, NULL )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+
+    TEST_ASSERT( mbedtls_poly1305_mac( NULL, src, 0, mac )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_mac( key, NULL, src_len, mac )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_mac( key, src, 0, NULL )
+                 == MBEDTLS_ERR_POLY1305_BAD_INPUT_DATA );
+    TEST_ASSERT( mbedtls_poly1305_mac( key, NULL, 0, mac )
+                 == 0 );
+
+    mbedtls_poly1305_free( &ctx );
+}
+/* END_CASE */
+
+/* BEGIN_CASE depends_on:MBEDTLS_SELF_TEST */
 void poly1305_selftest()
 {
     TEST_ASSERT( mbedtls_poly1305_self_test( 1 ) == 0 );