diff --git a/src/syzygy/tbprobe.cpp b/src/syzygy/tbprobe.cpp
index 56b8b86b..18527364 100644
--- a/src/syzygy/tbprobe.cpp
+++ b/src/syzygy/tbprobe.cpp
@@ -162,7 +162,7 @@ auto item(DTZPiece& e, int    , int  ) -> decltype(e)& { return e; }
 auto item(WDLPawn&  e, int stm, int f) -> decltype(e.file[stm][f])& { return e.file[stm][f]; }
 auto item(DTZPawn&  e, int    , int f) -> decltype(e.file[f])& { return e.file[f]; }
 
-const uint8_t MapA1D1D4[] = {
+const uint8_t MapA1D1D4[64] = {
     6, 0, 1, 2, 0, 0, 0, 0,
     0, 7, 3, 4, 0, 0, 0, 0,
     0, 0, 8, 5, 0, 0, 0, 0,
@@ -208,108 +208,7 @@ const uint8_t Invflap[] = {
     11, 19, 27, 35, 43, 51
 };
 
-const short KK_idx[10][64] = {
-    {
-        -1, -1, -1,  0,  1,  2,  3,  4,
-        -1, -1, -1,  5,  6,  7,  8,  9,
-        10, 11, 12, 13, 14, 15, 16, 17,
-        18, 19, 20, 21, 22, 23, 24, 25,
-        26, 27, 28, 29, 30, 31, 32, 33,
-        34, 35, 36, 37, 38, 39, 40, 41,
-        42, 43, 44, 45, 46, 47, 48, 49,
-        50, 51, 52, 53, 54, 55, 56, 57
-    },
-    {
-        58,  -1, -1, -1, 59, 60, 61, 62,
-        63,  -1, -1, -1, 64, 65, 66, 67,
-        68,  69, 70, 71, 72, 73, 74, 75,
-        76,  77, 78, 79, 80, 81, 82, 83,
-        84,  85, 86, 87, 88, 89, 90, 91,
-        92,  93, 94, 95, 96, 97, 98, 99,
-        100,101,102,103,104,105,106,107,
-        108,109,110,111,112,113,114,115
-    },
-    {
-        116,117, -1, -1, -1,118,119,120,
-        121,122, -1, -1, -1,123,124,125,
-        126,127,128,129,130,131,132,133,
-        134,135,136,137,138,139,140,141,
-        142,143,144,145,146,147,148,149,
-        150,151,152,153,154,155,156,157,
-        158,159,160,161,162,163,164,165,
-        166,167,168,169,170,171,172,173
-    },
-    {
-        174, -1, -1, -1,175,176,177,178,
-        179, -1, -1, -1,180,181,182,183,
-        184, -1, -1, -1,185,186,187,188,
-        189,190,191,192,193,194,195,196,
-        197,198,199,200,201,202,203,204,
-        205,206,207,208,209,210,211,212,
-        213,214,215,216,217,218,219,220,
-        221,222,223,224,225,226,227,228
-    },
-    {
-        229,230, -1, -1, -1,231,232,233,
-        234,235, -1, -1, -1,236,237,238,
-        239,240, -1, -1, -1,241,242,243,
-        244,245,246,247,248,249,250,251,
-        252,253,254,255,256,257,258,259,
-        260,261,262,263,264,265,266,267,
-        268,269,270,271,272,273,274,275,
-        276,277,278,279,280,281,282,283
-    },
-    {
-        284,285,286,287,288,289,290,291,
-        292,293, -1, -1, -1,294,295,296,
-        297,298, -1, -1, -1,299,300,301,
-        302,303, -1, -1, -1,304,305,306,
-        307,308,309,310,311,312,313,314,
-        315,316,317,318,319,320,321,322,
-        323,324,325,326,327,328,329,330,
-        331,332,333,334,335,336,337,338
-    },
-    {
-        -1, -1,339,340,341,342,343,344,
-        -1, -1,345,346,347,348,349,350,
-        -1, -1,441,351,352,353,354,355,
-        -1, -1, -1,442,356,357,358,359,
-        -1, -1, -1, -1,443,360,361,362,
-        -1, -1, -1, -1, -1,444,363,364,
-        -1, -1, -1, -1, -1, -1,445,365,
-        -1, -1, -1, -1, -1, -1, -1,446
-    },
-    {
-        -1, -1, -1,366,367,368,369,370,
-        -1, -1, -1,371,372,373,374,375,
-        -1, -1, -1,376,377,378,379,380,
-        -1, -1, -1,447,381,382,383,384,
-        -1, -1, -1, -1,448,385,386,387,
-        -1, -1, -1, -1, -1,449,388,389,
-        -1, -1, -1, -1, -1, -1,450,390,
-        -1, -1, -1, -1, -1, -1, -1,451
-    },
-    {
-        452,391,392,393,394,395,396,397,
-         -1, -1, -1, -1,398,399,400,401,
-         -1, -1, -1, -1,402,403,404,405,
-         -1, -1, -1, -1,406,407,408,409,
-         -1, -1, -1, -1,453,410,411,412,
-         -1, -1, -1, -1, -1,454,413,414,
-         -1, -1, -1, -1, -1, -1,455,415,
-         -1, -1, -1, -1, -1, -1, -1,456
-    },
-    {
-        457,416,417,418,419,420,421,422,
-         -1,458,423,424,425,426,427,428,
-         -1, -1, -1, -1, -1,429,430,431,
-         -1, -1, -1, -1, -1,432,433,434,
-         -1, -1, -1, -1, -1,435,436,437,
-         -1, -1, -1, -1, -1,459,438,439,
-         -1, -1, -1, -1, -1, -1,460,440,
-         -1, -1, -1, -1, -1, -1, -1,461
-    }
-};
+int KK_idx[10][64];
 
 const uint8_t WDL_MAGIC[] = { 0x71, 0xE8, 0x23, 0x5D };
 const uint8_t DTZ_MAGIC[] = { 0xD7, 0x66, 0x0C, 0xA5 };
@@ -1689,6 +1588,34 @@ void Tablebases::init(const std::string& paths)
         }
     }
 
+    // Compute KK_idx[] that encodes all the 461 possible legal positions of a couple of
+    // kings where first king is on a1-d1-d4 triangle. When first king is on the a1-d4
+    // diagonal, second king is assumed not to be above the a1-h8 diagonal.
+    int code = 0;
+    std::vector<std::pair<int, Square>> bothOnDiagonal;
+
+    for (int idx = 0; idx < 10; idx++)
+        for (Square s1 = SQ_A1; s1 <= SQ_H8; ++s1)
+            if (idx == MapA1D1D4[s1] && (idx || s1 == SQ_B1)) // SQ_B1 is mapped to 0
+                for (Square s2 = SQ_A1; s2 <= SQ_H8; ++s2)
+                {
+                    if ((StepAttacksBB[KING][s1] | s1) & s2) // Illegal position
+                        KK_idx[idx][s2] = -1;
+
+                    else if (!off_A1H8(s1) && off_A1H8(s2) > 0)
+                        KK_idx[idx][s2] = -1; // First king on diagonal, second above
+
+                    else if (!off_A1H8(s1) && !off_A1H8(s2))
+                        bothOnDiagonal.push_back(std::make_pair(idx, s2));
+
+                    else
+                        KK_idx[idx][s2] = code++;
+                }
+
+    // Legal positions with both kings on diagonal are encoded as last ones
+    for (auto p : bothOnDiagonal)
+        KK_idx[p.first][p.second] = code++;
+
     for (PieceType p1 = PAWN; p1 < KING; ++p1) {
         WDLHash.insert({KING, p1, KING});