diff --git a/ChangeLog.d/mbedtls_debug_print_mpi.txt b/ChangeLog.d/mbedtls_debug_print_mpi.txt
new file mode 100644
index 0000000..895ab18
--- /dev/null
+++ b/ChangeLog.d/mbedtls_debug_print_mpi.txt
@@ -0,0 +1,3 @@
+Bugfix
+   * Fix a crash in mbedtls_mpi_debug_mpi on a bignum having 0 limbs.
+     Reported by lhuang04 in #4578. Fixes #4608.
diff --git a/library/debug.c b/library/debug.c
index 5f06d0d..9caa361 100644
--- a/library/debug.c
+++ b/library/debug.c
@@ -261,8 +261,8 @@
                       const char *text, const mbedtls_mpi *X )
 {
     char str[DEBUG_BUF_SIZE];
-    int j, k, zeros = 1;
-    size_t i, n, idx = 0;
+    size_t bitlen;
+    size_t idx = 0;
 
     if( NULL == ssl              ||
         NULL == ssl->conf        ||
@@ -273,55 +273,43 @@
         return;
     }
 
-    for( n = X->n - 1; n > 0; n-- )
-        if( X->p[n] != 0 )
-            break;
+    bitlen = mbedtls_mpi_bitlen( X );
 
-    for( j = ( sizeof(mbedtls_mpi_uint) << 3 ) - 1; j >= 0; j-- )
-        if( ( ( X->p[n] >> j ) & 1 ) != 0 )
-            break;
-
-    mbedtls_snprintf( str + idx, sizeof( str ) - idx, "value of '%s' (%d bits) is:\n",
-              text, (int) ( ( n * ( sizeof(mbedtls_mpi_uint) << 3 ) ) + j + 1 ) );
-
+    mbedtls_snprintf( str, sizeof( str ), "value of '%s' (%u bits) is:\n",
+                      text, (unsigned) bitlen );
     debug_send_line( ssl, level, file, line, str );
 
-    idx = 0;
-    for( i = n + 1, j = 0; i > 0; i-- )
+    if( bitlen == 0 )
     {
-        if( zeros && X->p[i - 1] == 0 )
-            continue;
-
-        for( k = sizeof( mbedtls_mpi_uint ) - 1; k >= 0; k-- )
+        str[0] = ' '; str[1] = '0'; str[2] = '0';
+        idx = 3;
+    }
+    else
+    {
+        int n;
+        for( n = (int) ( ( bitlen - 1 ) / 8 ); n >= 0; n-- )
         {
-            if( zeros && ( ( X->p[i - 1] >> ( k << 3 ) ) & 0xFF ) == 0 )
-                continue;
-            else
-                zeros = 0;
-
-            if( j % 16 == 0 )
+            size_t limb_offset = n / sizeof( mbedtls_mpi_uint );
+            size_t offset_in_limb = n % sizeof( mbedtls_mpi_uint );
+            unsigned char octet =
+                ( X->p[limb_offset] >> ( offset_in_limb * 8 ) ) & 0xff;
+            mbedtls_snprintf( str + idx, sizeof( str ) - idx, " %02x", octet );
+            idx += 3;
+            /* Wrap lines after 16 octets that each take 3 columns */
+            if( idx >= 3 * 16 )
             {
-                if( j > 0 )
-                {
-                    mbedtls_snprintf( str + idx, sizeof( str ) - idx, "\n" );
-                    debug_send_line( ssl, level, file, line, str );
-                    idx = 0;
-                }
+                mbedtls_snprintf( str + idx, sizeof( str ) - idx, "\n" );
+                debug_send_line( ssl, level, file, line, str );
+                idx = 0;
             }
-
-            idx += mbedtls_snprintf( str + idx, sizeof( str ) - idx, " %02x", (unsigned int)
-                             ( X->p[i - 1] >> ( k << 3 ) ) & 0xFF );
-
-            j++;
         }
-
     }
 
-    if( zeros == 1 )
-        idx += mbedtls_snprintf( str + idx, sizeof( str ) - idx, " 00" );
-
-    mbedtls_snprintf( str + idx, sizeof( str ) - idx, "\n" );
-    debug_send_line( ssl, level, file, line, str );
+    if( idx != 0 )
+    {
+        mbedtls_snprintf( str + idx, sizeof( str ) - idx, "\n" );
+        debug_send_line( ssl, level, file, line, str );
+    }
 }
 #endif /* MBEDTLS_BIGNUM_C */
 
diff --git a/tests/suites/test_suite_debug.data b/tests/suites/test_suite_debug.data
index eb99b79..6d57442 100644
--- a/tests/suites/test_suite_debug.data
+++ b/tests/suites/test_suite_debug.data
@@ -37,6 +37,27 @@
 Debug print buffer #5
 mbedtls_debug_print_buf:"MyFile":999:"Test return value":"000102030405060708090A0B0C0D0E0F101112131415161718191A1B1C1D1E1F202122232425262728292A2B2C2D2E2F30":"MyFile(0999)\: dumping 'Test return value' (49 bytes)\nMyFile(0999)\: 0000\:  00 01 02 03 04 05 06 07 08 09 0a 0b 0c 0d 0e 0f  ................\nMyFile(0999)\: 0010\:  10 11 12 13 14 15 16 17 18 19 1a 1b 1c 1d 1e 1f  ................\nMyFile(0999)\: 0020\:  20 21 22 23 24 25 26 27 28 29 2a 2b 2c 2d 2e 2f   !"#$%&'()*+,-./\nMyFile(0999)\: 0030\:  30                                               0\n"
 
+Debug print mbedtls_mpi: 0 (empty representation)
+mbedtls_debug_print_mpi:16:"":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (0 bits) is\:\nMyFile(0999)\:  00\n"
+
+Debug print mbedtls_mpi: 0 (non-empty representation)
+mbedtls_debug_print_mpi:16:"00000000000000":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (0 bits) is\:\nMyFile(0999)\:  00\n"
+
+Debug print mbedtls_mpi #2: 3 bits
+mbedtls_debug_print_mpi:16:"00000000000007":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (3 bits) is\:\nMyFile(0999)\:  07\n"
+
+Debug print mbedtls_mpi: 49 bits
+mbedtls_debug_print_mpi:16:"01020304050607":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (49 bits) is\:\nMyFile(0999)\:  01 02 03 04 05 06 07\n"
+
+Debug print mbedtls_mpi: 759 bits
+mbedtls_debug_print_mpi:16:"0000000000000000000000000000000000000000000000000000000041379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (759 bits) is\:\nMyFile(0999)\:  41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a 14\nMyFile(0999)\:  2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90 ff\nMyFile(0999)\:  e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c 09\nMyFile(0999)\:  18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89 af\nMyFile(0999)\:  48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b 52\nMyFile(0999)\:  62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
+
+Debug print mbedtls_mpi: 764 bits #1
+mbedtls_debug_print_mpi:16:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (764 bits) is\:\nMyFile(0999)\:  09 41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a\nMyFile(0999)\:  14 2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90\nMyFile(0999)\:  ff e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c\nMyFile(0999)\:  09 18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89\nMyFile(0999)\:  af 48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b\nMyFile(0999)\:  52 62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
+
+Debug print mbedtls_mpi: 764 bits #2
+mbedtls_debug_print_mpi:16:"0000000000000000000000000000000000000000000000000000000941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (764 bits) is\:\nMyFile(0999)\:  09 41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a\nMyFile(0999)\:  14 2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90\nMyFile(0999)\:  ff e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c\nMyFile(0999)\:  09 18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89\nMyFile(0999)\:  af 48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b\nMyFile(0999)\:  52 62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
+
 Debug print certificate #1 (RSA)
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_BASE64_C:MBEDTLS_RSA_C:MBEDTLS_SHA1_C
 mbedtls_debug_print_crt:"data_files/server1.crt":"MyFile":999:"PREFIX_":"MyFile(0999)\: PREFIX_ #1\:\nMyFile(0999)\: cert. version     \: 3\nMyFile(0999)\: serial number     \: 01\nMyFile(0999)\: issuer name       \: C=NL, O=PolarSSL, CN=PolarSSL Test CA\nMyFile(0999)\: subject name      \: C=NL, O=PolarSSL, CN=PolarSSL Server 1\nMyFile(0999)\: issued  on        \: 2019-02-10 14\:44\:06\nMyFile(0999)\: expires on        \: 2029-02-10 14\:44\:06\nMyFile(0999)\: signed using      \: RSA with SHA1\nMyFile(0999)\: RSA key size      \: 2048 bits\nMyFile(0999)\: basic constraints \: CA=false\nMyFile(0999)\: value of 'crt->rsa.N' (2048 bits) is\:\nMyFile(0999)\:  a9 02 1f 3d 40 6a d5 55 53 8b fd 36 ee 82 65 2e\nMyFile(0999)\:  15 61 5e 89 bf b8 e8 45 90 db ee 88 16 52 d3 f1\nMyFile(0999)\:  43 50 47 96 12 59 64 87 6b fd 2b e0 46 f9 73 be\nMyFile(0999)\:  dd cf 92 e1 91 5b ed 66 a0 6f 89 29 79 45 80 d0\nMyFile(0999)\:  83 6a d5 41 43 77 5f 39 7c 09 04 47 82 b0 57 39\nMyFile(0999)\:  70 ed a3 ec 15 19 1e a8 33 08 47 c1 05 42 a9 fd\nMyFile(0999)\:  4c c3 b4 df dd 06 1f 4d 10 51 40 67 73 13 0f 40\nMyFile(0999)\:  f8 6d 81 25 5f 0a b1 53 c6 30 7e 15 39 ac f9 5a\nMyFile(0999)\:  ee 7f 92 9e a6 05 5b e7 13 97 85 b5 23 92 d9 d4\nMyFile(0999)\:  24 06 d5 09 25 89 75 07 dd a6 1a 8f 3f 09 19 be\nMyFile(0999)\:  ad 65 2c 64 eb 95 9b dc fe 41 5e 17 a6 da 6c 5b\nMyFile(0999)\:  69 cc 02 ba 14 2c 16 24 9c 4a dc cd d0 f7 52 67\nMyFile(0999)\:  73 f1 2d a0 23 fd 7e f4 31 ca 2d 70 ca 89 0b 04\nMyFile(0999)\:  db 2e a6 4f 70 6e 9e ce bd 58 89 e2 53 59 9e 6e\nMyFile(0999)\:  5a 92 65 e2 88 3f 0c 94 19 a3 dd e5 e8 9d 95 13\nMyFile(0999)\:  ed 29 db ab 70 12 dc 5a ca 6b 17 ab 52 82 54 b1\nMyFile(0999)\: value of 'crt->rsa.E' (17 bits) is\:\nMyFile(0999)\:  01 00 01\n"
@@ -44,21 +65,3 @@
 Debug print certificate #2 (EC)
 depends_on:MBEDTLS_PEM_PARSE_C:MBEDTLS_BASE64_C:MBEDTLS_ECDSA_C:MBEDTLS_ECP_C:MBEDTLS_ECP_DP_SECP384R1_ENABLED:MBEDTLS_SHA256_C
 mbedtls_debug_print_crt:"data_files/test-ca2.crt":"MyFile":999:"PREFIX_":"MyFile(0999)\: PREFIX_ #1\:\nMyFile(0999)\: cert. version     \: 3\nMyFile(0999)\: serial number     \: C1\:43\:E2\:7E\:62\:43\:CC\:E8\nMyFile(0999)\: issuer name       \: C=NL, O=PolarSSL, CN=Polarssl Test EC CA\nMyFile(0999)\: subject name      \: C=NL, O=PolarSSL, CN=Polarssl Test EC CA\nMyFile(0999)\: issued  on        \: 2019-02-10 14\:44\:00\nMyFile(0999)\: expires on        \: 2029-02-10 14\:44\:00\nMyFile(0999)\: signed using      \: ECDSA with SHA256\nMyFile(0999)\: EC key size       \: 384 bits\nMyFile(0999)\: basic constraints \: CA=true\nMyFile(0999)\: value of 'crt->eckey.Q(X)' (384 bits) is\:\nMyFile(0999)\:  c3 da 2b 34 41 37 58 2f 87 56 fe fc 89 ba 29 43\nMyFile(0999)\:  4b 4e e0 6e c3 0e 57 53 33 39 58 d4 52 b4 91 95\nMyFile(0999)\:  39 0b 23 df 5f 17 24 62 48 fc 1a 95 29 ce 2c 2d\nMyFile(0999)\: value of 'crt->eckey.Q(Y)' (384 bits) is\:\nMyFile(0999)\:  87 c2 88 52 80 af d6 6a ab 21 dd b8 d3 1c 6e 58\nMyFile(0999)\:  b8 ca e8 b2 69 8e f3 41 ad 29 c3 b4 5f 75 a7 47\nMyFile(0999)\:  6f d5 19 29 55 69 9a 53 3b 20 b4 66 16 60 33 1e\n"
-
-Debug print mbedtls_mpi #1
-mbedtls_debug_print_mpi:16:"01020304050607":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (49 bits) is\:\nMyFile(0999)\:  01 02 03 04 05 06 07\n"
-
-Debug print mbedtls_mpi #2
-mbedtls_debug_print_mpi:16:"00000000000007":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (3 bits) is\:\nMyFile(0999)\:  07\n"
-
-Debug print mbedtls_mpi #3
-mbedtls_debug_print_mpi:16:"00000000000000":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (0 bits) is\:\nMyFile(0999)\:  00\n"
-
-Debug print mbedtls_mpi #4
-mbedtls_debug_print_mpi:16:"0941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (764 bits) is\:\nMyFile(0999)\:  09 41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a\nMyFile(0999)\:  14 2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90\nMyFile(0999)\:  ff e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c\nMyFile(0999)\:  09 18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89\nMyFile(0999)\:  af 48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b\nMyFile(0999)\:  52 62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
-
-Debug print mbedtls_mpi #5
-mbedtls_debug_print_mpi:16:"0000000000000000000000000000000000000000000000000000000941379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (764 bits) is\:\nMyFile(0999)\:  09 41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a\nMyFile(0999)\:  14 2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90\nMyFile(0999)\:  ff e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c\nMyFile(0999)\:  09 18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89\nMyFile(0999)\:  af 48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b\nMyFile(0999)\:  52 62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
-
-Debug print mbedtls_mpi #6
-mbedtls_debug_print_mpi:16:"0000000000000000000000000000000000000000000000000000000041379d00fed1491fe15df284dfde4a142f68aa8d412023195cee66883e6290ffe703f4ea5963bf212713cee46b107c09182b5edcd955adac418bf4918e2889af48e1099d513830cec85c26ac1e158b52620e33ba8692f893efbb2f958b4424":"MyFile":999:"VALUE":"MyFile(0999)\: value of 'VALUE' (759 bits) is\:\nMyFile(0999)\:  41 37 9d 00 fe d1 49 1f e1 5d f2 84 df de 4a 14\nMyFile(0999)\:  2f 68 aa 8d 41 20 23 19 5c ee 66 88 3e 62 90 ff\nMyFile(0999)\:  e7 03 f4 ea 59 63 bf 21 27 13 ce e4 6b 10 7c 09\nMyFile(0999)\:  18 2b 5e dc d9 55 ad ac 41 8b f4 91 8e 28 89 af\nMyFile(0999)\:  48 e1 09 9d 51 38 30 ce c8 5c 26 ac 1e 15 8b 52\nMyFile(0999)\:  62 0e 33 ba 86 92 f8 93 ef bb 2f 95 8b 44 24\n"
diff --git a/tests/suites/test_suite_debug.function b/tests/suites/test_suite_debug.function
index 377d630..0e663c6 100644
--- a/tests/suites/test_suite_debug.function
+++ b/tests/suites/test_suite_debug.function
@@ -179,7 +179,9 @@
 
     TEST_ASSERT( mbedtls_ssl_setup( &ssl, &conf ) == 0 );
 
-    TEST_ASSERT( mbedtls_mpi_read_string( &val, radix, value ) == 0 );
+    /* If value is empty, keep val->n == 0. */
+    if( value[0] != 0 )
+        TEST_ASSERT( mbedtls_mpi_read_string( &val, radix, value ) == 0 );
 
     mbedtls_ssl_conf_dbg( &conf, string_debug, &buffer);