diff --git a/ChangeLog.d/mpi_read_negative_zero.txt b/ChangeLog.d/mpi_read_negative_zero.txt
new file mode 100644
index 000000000..e338de70b
--- /dev/null
+++ b/ChangeLog.d/mpi_read_negative_zero.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * mbedtls_mpi_read_string on "-0" produced an MPI object that was not treated
+     as equal to 0 in all cases. Fix it to produce the same object as "0".
diff --git a/library/bignum.c b/library/bignum.c
index f133f6c13..bd352e1bb 100644
--- a/library/bignum.c
+++ b/library/bignum.c
@@ -500,6 +500,7 @@ int mbedtls_mpi_read_string( mbedtls_mpi *X, int radix, const char *s )
 {
     int ret;
     size_t i, j, slen, n;
+    int sign = 1;
     mbedtls_mpi_uint d;
     mbedtls_mpi T;
     MPI_VALIDATE_RET( X != NULL );
@@ -510,6 +511,12 @@ int mbedtls_mpi_read_string( mbedtls_mpi *X, int radix, const char *s )
 
     mbedtls_mpi_init( &T );
 
+    if( s[0] == '-' )
+    {
+        ++s;
+        sign = -1;
+    }
+
     slen = strlen( s );
 
     if( radix == 16 )
@@ -524,12 +531,6 @@ int mbedtls_mpi_read_string( mbedtls_mpi *X, int radix, const char *s )
 
         for( i = slen, j = 0; i > 0; i--, j++ )
         {
-            if( i == 1 && s[i - 1] == '-' )
-            {
-                X->s = -1;
-                break;
-            }
-
             MBEDTLS_MPI_CHK( mpi_get_digit( &d, radix, s[i - 1] ) );
             X->p[j / ( 2 * ciL )] |= d << ( ( j % ( 2 * ciL ) ) << 2 );
         }
@@ -540,26 +541,15 @@ int mbedtls_mpi_read_string( mbedtls_mpi *X, int radix, const char *s )
 
         for( i = 0; i < slen; i++ )
         {
-            if( i == 0 && s[i] == '-' )
-            {
-                X->s = -1;
-                continue;
-            }
-
             MBEDTLS_MPI_CHK( mpi_get_digit( &d, radix, s[i] ) );
             MBEDTLS_MPI_CHK( mbedtls_mpi_mul_int( &T, X, radix ) );
-
-            if( X->s == 1 )
-            {
-                MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( X, &T, d ) );
-            }
-            else
-            {
-                MBEDTLS_MPI_CHK( mbedtls_mpi_sub_int( X, &T, d ) );
-            }
+            MBEDTLS_MPI_CHK( mbedtls_mpi_add_int( X, &T, d ) );
         }
     }
 
+    if( sign < 0 && mbedtls_mpi_bitlen( X ) != 0 )
+        X->s = -1;
+
 cleanup:
 
     mbedtls_mpi_free( &T );
diff --git a/library/ecp_curves.c b/library/ecp_curves.c
index b04596b56..396734d17 100644
--- a/library/ecp_curves.c
+++ b/library/ecp_curves.c
@@ -1048,13 +1048,13 @@ static inline void sub32( uint32_t *dst, uint32_t src, signed char *carry )
 
 /*
  * If the result is negative, we get it in the form
- * c * 2^(bits + 32) + N, with c negative and N positive shorter than 'bits'
+ * c * 2^bits + N, with c negative and N positive shorter than 'bits'
  */
 static inline int fix_negative( mbedtls_mpi *N, signed char c, mbedtls_mpi *C, size_t bits )
 {
     int ret;
 
-    /* C = - c * 2^(bits + 32) */
+    /* C = - c * 2^bits */
 #if !defined(MBEDTLS_HAVE_INT64)
     ((void) bits);
 #else
diff --git a/tests/suites/test_suite_ecp.data b/tests/suites/test_suite_ecp.data
index 2c25cd7c4..398ba597c 100644
--- a/tests/suites/test_suite_ecp.data
+++ b/tests/suites/test_suite_ecp.data
@@ -344,6 +344,14 @@ ECP point multiplication rng fail Curve25519
 depends_on:MBEDTLS_ECP_DP_CURVE25519_ENABLED
 ecp_test_mul_rng:MBEDTLS_ECP_DP_CURVE25519:"5AC99F33632E5A768DE7E81BF854C27C46E3FBF2ABBACD29EC4AFF517369C660"
 
+ECP point muladd secp256r1 #1
+depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+ecp_muladd:MBEDTLS_ECP_DP_SECP256R1:"01":"04e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e0e1ff20e1ffe120e1e1e173287170a761308491683e345cacaebb500c96e1a7bbd37772968b2c951f0579":"01":"04e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1ffffffff20e120e1e1e1e13a4e135157317b79d4ecf329fed4f9eb00dc67dbddae33faca8b6d8a0255b5ce":"04fab65e09aa5dd948320f86246be1d3fc571e7f799d9005170ed5cc868b67598431a668f96aa9fd0b0eb15f0edf4c7fe1be2885eadcb57e3db4fdd093585d3fa6"
+
+ECP point muladd secp256r1 #2
+depends_on:MBEDTLS_ECP_DP_SECP256R1_ENABLED
+ecp_muladd:MBEDTLS_ECP_DP_SECP256R1:"01":"04e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1ffffffff20e120e1e1e1e13a4e135157317b79d4ecf329fed4f9eb00dc67dbddae33faca8b6d8a0255b5ce":"01":"04e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e1e0e1ff20e1ffe120e1e1e173287170a761308491683e345cacaebb500c96e1a7bbd37772968b2c951f0579":"04fab65e09aa5dd948320f86246be1d3fc571e7f799d9005170ed5cc868b67598431a668f96aa9fd0b0eb15f0edf4c7fe1be2885eadcb57e3db4fdd093585d3fa6"
+
 ECP test vectors secp192k1
 depends_on:MBEDTLS_ECP_DP_SECP192K1_ENABLED
 ecp_test_vect:MBEDTLS_ECP_DP_SECP192K1:"D1E13A359F6E0F0698791938E6D60246030AE4B0D8D4E9DE":"281BCA982F187ED30AD5E088461EBE0A5FADBB682546DF79":"3F68A8E9441FB93A4DD48CB70B504FCC9AA01902EF5BE0F3":"BE97C5D2A1A94D081E3FACE53E65A27108B7467BDF58DE43":"5EB35E922CD693F7947124F5920022C4891C04F6A8B8DCB2":"60ECF73D0FC43E0C42E8E155FFE39F9F0B531F87B34B6C3C":"372F5C5D0E18313C82AEF940EC3AFEE26087A46F1EBAE923":"D5A9F9182EC09CEAEA5F57EA10225EC77FA44174511985FD"
diff --git a/tests/suites/test_suite_ecp.function b/tests/suites/test_suite_ecp.function
index e37a017a6..9c90e9c2a 100644
--- a/tests/suites/test_suite_ecp.function
+++ b/tests/suites/test_suite_ecp.function
@@ -699,6 +699,52 @@ exit:
 }
 /* END_CASE */
 
+/* BEGIN_CASE depends_on:MBEDTLS_ECP_SHORT_WEIERSTRASS_ENABLED */
+void ecp_muladd( int id,
+                 data_t *u1_bin, data_t *P1_bin,
+                 data_t *u2_bin, data_t *P2_bin,
+                 data_t *expected_result )
+{
+    /* Compute R = u1 * P1 + u2 * P2 */
+    mbedtls_ecp_group grp;
+    mbedtls_ecp_point P1, P2, R;
+    mbedtls_mpi u1, u2;
+    uint8_t actual_result[MBEDTLS_ECP_MAX_PT_LEN];
+    size_t len;
+
+    mbedtls_ecp_group_init( &grp );
+    mbedtls_ecp_point_init( &P1 );
+    mbedtls_ecp_point_init( &P2 );
+    mbedtls_ecp_point_init( &R );
+    mbedtls_mpi_init( &u1 );
+    mbedtls_mpi_init( &u2 );
+
+    TEST_EQUAL( 0, mbedtls_ecp_group_load( &grp, id ) );
+    TEST_EQUAL( 0, mbedtls_mpi_read_binary( &u1, u1_bin->x, u1_bin->len ) );
+    TEST_EQUAL( 0, mbedtls_mpi_read_binary( &u2, u2_bin->x, u2_bin->len ) );
+    TEST_EQUAL( 0, mbedtls_ecp_point_read_binary( &grp, &P1,
+                                                  P1_bin->x, P1_bin->len ) );
+    TEST_EQUAL( 0, mbedtls_ecp_point_read_binary( &grp, &P2,
+                                                  P2_bin->x, P2_bin->len ) );
+
+    TEST_EQUAL( 0, mbedtls_ecp_muladd( &grp, &R, &u1, &P1, &u2, &P2 ) );
+    TEST_EQUAL( 0, mbedtls_ecp_point_write_binary(
+                    &grp, &R, MBEDTLS_ECP_PF_UNCOMPRESSED,
+                    &len, actual_result, sizeof( actual_result ) ) );
+
+    ASSERT_COMPARE( expected_result->x, expected_result->len,
+                    actual_result, len );
+
+exit:
+    mbedtls_ecp_group_free( &grp );
+    mbedtls_ecp_point_free( &P1 );
+    mbedtls_ecp_point_free( &P2 );
+    mbedtls_ecp_point_free( &R );
+    mbedtls_mpi_free( &u1 );
+    mbedtls_mpi_free( &u2 );
+}
+/* END_CASE */
+
 /* BEGIN_CASE */
 void ecp_fast_mod( int id, char * N_str )
 {
diff --git a/tests/suites/test_suite_mpi.data b/tests/suites/test_suite_mpi.data
index 5229253f6..b7f7ee53d 100644
--- a/tests/suites/test_suite_mpi.data
+++ b/tests/suites/test_suite_mpi.data
@@ -10,21 +10,39 @@ mpi_null:
 Base test mpi_read_write_string #1
 mpi_read_write_string:10:"128":10:"128":100:0:0
 
+Base test mpi_read_write_string #1 (Leading 0)
+mpi_read_write_string:10:"0128":10:"128":100:0:0
+
 Base test mpi_read_write_string #2
 mpi_read_write_string:10:"128":16:"80":100:0:0
 
-Base test mpi_read_write_string #3 (Read zero)
+Base test mpi_read_write_string #3 (Read zero decimal)
 mpi_read_write_string:10:"0":10:"0":100:0:0
 
+Base test mpi_read_write_string #3 (Read zero hex)
+mpi_read_write_string:16:"0":16:"00":100:0:0
+
+Base test mpi_read_write_string #3 (Read minus zero decimal)
+mpi_read_write_string:10:"-0":10:"0":100:0:0
+
+Base test mpi_read_write_string #3 (Read minus zero hex)
+mpi_read_write_string:16:"-0":16:"00":100:0:0
+
 Base test mpi_read_write_string #3 (Negative decimal)
 mpi_read_write_string:10:"-23":10:"-23":100:0:0
 
-Base test mpi_read_write_string #3 (Negative hex)
+Base test mpi_read_write_string #3 (Negative decimal, leading 0)
+mpi_read_write_string:10:"-023":10:"-23":100:0:0
+
+Base test mpi_read_write_string #3 (Negative hex -> decimal)
 mpi_read_write_string:16:"-20":10:"-32":100:0:0
 
-Base test mpi_read_write_string #3 (Negative decimal)
+Base test mpi_read_write_string #3 (Negative hex)
 mpi_read_write_string:16:"-23":16:"-23":100:0:0
 
+Base test mpi_read_write_string #3 (Negative hex, leading 0)
+mpi_read_write_string:16:"-023":16:"-23":100:0:0
+
 Base test mpi_read_write_string #4 (Buffer just fits)
 mpi_read_write_string:16:"-4":4:"-10":4:0:0
 
@@ -49,12 +67,18 @@ mpi_read_write_string:10:"29":15:"1e":100:0:0
 Test mpi_read_write_string #7
 mpi_read_write_string:10:"56125680981752282334141896320372489490613963693556392520816017892111350604111697682705498319512049040516698827829292076808006940873974979584527073481012636016353913462376755556720019831187364993587901952757307830896531678727717924":16:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":200:0:0
 
-Test mpi_read_write_string #8 (Empty MPI -> hex)
+Test mpi_read_write_string #8 (Empty MPI hex -> hex)
 mpi_read_write_string:16:"":16:"00":4:0:0
 
-Test mpi_read_write_string #9 (Empty MPI -> dec)
+Test mpi_read_write_string #9 (Empty MPI hex -> dec)
 mpi_read_write_string:16:"":10:"0":4:0:0
 
+Test mpi_read_write_string #8 (Empty MPI dec -> hex)
+mpi_read_write_string:10:"":16:"00":4:0:0
+
+Test mpi_read_write_string #9 (Empty MPI dec -> dec)
+mpi_read_write_string:10:"":10:"0":4:0:0
+
 Test mpi_write_string #10 (Negative hex with odd number of digits)
 mpi_read_write_string:16:"-1":16:"":3:0:MBEDTLS_ERR_MPI_BUFFER_TOO_SMALL