diff --git a/src/datagen/datagen.cpp b/src/datagen/datagen.cpp
index 2e4e45d..7345ad6 100644
--- a/src/datagen/datagen.cpp
+++ b/src/datagen/datagen.cpp
@@ -85,7 +85,7 @@ namespace stoat::datagen {
                 const auto sennichite = newPos.testSennichite(false, keyHistory);
                 keyHistory.pop_back();
 
-                if (sennichite != SennichiteStatus::kWin) {
+                if (sennichite != SennichiteStatus::kWin || sennichite != SennichiteStatus::kLose) {
                     return move;
                 }
 
@@ -240,7 +240,7 @@ namespace stoat::datagen {
                     if (sennichite == SennichiteStatus::kDraw) {
                         outcome = format::Outcome::kDraw;
                         break;
-                    } else if (sennichite == SennichiteStatus::kWin) {
+                    } else if (sennichite == SennichiteStatus::kWin || sennichite == SennichiteStatus::kLose) {
                         const std::scoped_lock lock{s_printMutex};
 
                         auto& errStream = getErrStream(outDir);
diff --git a/src/position.cpp b/src/position.cpp
index a73196a..bf3a0a1 100644
--- a/src/position.cpp
+++ b/src/position.cpp
@@ -300,12 +300,12 @@ namespace stoat {
 
     SennichiteStatus Position::testSennichite(bool cuteChessWorkaround, std::span<const u64> keyHistory, i32 limit)
         const {
-        const auto end = std::max(0, static_cast<i32>(keyHistory.size()) - limit - 1);
+        const auto end = std::min(static_cast<i32>(keyHistory.size()), limit);
 
         i32 repetitions = 1;
 
-        for (i32 i = static_cast<i32>(keyHistory.size()) - 4; i >= end; i -= 2) {
-            if (keyHistory[i] == key()) {
+        for (i32 i = 4; i <= end; i += 2) {
+            if (keyHistory[keyHistory.size() - i] == key()) {
                 --repetitions;
                 if (repetitions == 0) {
                     // Older cutechess versions do not handle perpetuals
@@ -313,7 +313,13 @@ namespace stoat {
                     if (cuteChessWorkaround) {
                         return isInCheck() ? SennichiteStatus::kWin : SennichiteStatus::kDraw;
                     } else {
-                        return m_consecutiveChecks[stm().idx()] >= 2 ? SennichiteStatus::kWin : SennichiteStatus::kDraw;
+                        if (i / 2 <= m_consecutiveChecks[stm().idx()]) {
+                            return SennichiteStatus::kWin;
+                        } else if (i / 2 <= m_consecutiveChecks[stm().flip().idx()]) {
+                            return SennichiteStatus::kLose;
+                        } else {
+                            return SennichiteStatus::kDraw;
+                        }
                     }
                 }
             }
diff --git a/src/position.h b/src/position.h
index 54ae2e3..5e20a93 100644
--- a/src/position.h
+++ b/src/position.h
@@ -100,7 +100,8 @@ namespace stoat {
     enum class SennichiteStatus {
         kNone = 0,
         kDraw,
-        kWin, // perpetual check by opponent
+        kWin,  // perpetual check by opponent
+        kLose, // perpetual check
     };
 
     namespace eval::nnue {
diff --git a/src/search.cpp b/src/search.cpp
index c8ca88a..808bcb3 100644
--- a/src/search.cpp
+++ b/src/search.cpp
@@ -610,10 +610,13 @@ namespace stoat {
             Score score;
 
             if (sennichite == SennichiteStatus::kWin) {
-                // illegal perpetual
                 --legalMoves;
                 continue;
-            } else if (sennichite == SennichiteStatus::kDraw) {
+            } else if (sennichite == SennichiteStatus::kLose) {
+                score = kScoreMate - ply - 1;
+                goto skipSearch;
+            }
+            else if (sennichite == SennichiteStatus::kDraw) {
                 score = drawScore(thread.loadNodes());
                 goto skipSearch;
             } else if (pos.isEnteringKingsWin()) {
@@ -776,8 +779,9 @@ namespace stoat {
             Score score;
 
             if (sennichite == SennichiteStatus::kWin) {
-                // illegal perpetual
                 continue;
+            } else if (sennichite == SennichiteStatus::kLose) {
+                score = kScoreMate - ply - 1;
             } else if (sennichite == SennichiteStatus::kDraw) {
                 score = drawScore(thread.loadNodes());
             } else {
diff --git a/version.txt b/version.txt
index 71fb8a1..3234805 100644
--- a/version.txt
+++ b/version.txt
@@ -1 +1 @@
-0.1.100
+0.1.101