diff --git a/contrib/lfalloc/src/lf_allocX64.h b/contrib/lfalloc/src/lf_allocX64.h
index 2c4cf3f1021..12190f0712f 100644
--- a/contrib/lfalloc/src/lf_allocX64.h
+++ b/contrib/lfalloc/src/lf_allocX64.h
@@ -358,8 +358,15 @@ static char* AllocWithMMap(uintptr_t sz, EMMapMode mode) {
     }
 #if defined(USE_LFALLOC_RANDOM_HINT)
     static thread_local std::mt19937_64 generator(std::random_device{}());
-    std::uniform_int_distribution<intptr_t> distr(areaStart, areaFinish / 2);
-    char* largeBlock = (char*)mmap(reinterpret_cast<void*>(distr(generator)), sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+    std::uniform_int_distribution<intptr_t> distr(areaStart, areaFinish - sz - 1);
+    char* largeBlock;
+    static constexpr size_t MaxAttempts = 100;
+    size_t attempt = 0;
+    do
+    {
+        largeBlock = (char*)mmap(reinterpret_cast<void*>(distr(generator)), sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
+        ++attempt;
+    } while (uintptr_t(((char*)largeBlock - ALLOC_START) + sz) >= areaFinish && attempt < MaxAttempts && munmap(largeBlock, sz) == 0);
 #else
     char* largeBlock = (char*)mmap(0, sz, PROT_READ | PROT_WRITE, MAP_PRIVATE | MAP_ANON, -1, 0);
 #endif