diff --git a/lib/plugins/ray_trace.js b/lib/plugins/ray_trace.js
index e45c83f019..1436c3673f 100644
--- a/lib/plugins/ray_trace.js
+++ b/lib/plugins/ray_trace.js
@@ -55,8 +55,11 @@ module.exports = (bot) => {
   }
 
   bot.blockAtEntityCursor = (entity = bot.entity, maxDistance = 256, matcher = null) => {
-    if (!entity.position || !entity.height || !entity.pitch || !entity.yaw) return null
+    if (!entity.position) return null
     const { position, height, pitch, yaw } = entity
+    // Number.isFinite (rather than truthiness) so a legitimate 0 yaw or pitch
+    // is not mistaken for a missing value. See issue #3935.
+    if (!Number.isFinite(height) || !Number.isFinite(pitch) || !Number.isFinite(yaw)) return null
 
     const eyePosition = position.offset(0, height, 0)
     const viewDirection = getViewDirection(pitch, yaw)
diff --git a/test/externalTests/rayTrace.js b/test/externalTests/rayTrace.js
index 8d252e3c52..31c101c27f 100644
--- a/test/externalTests/rayTrace.js
+++ b/test/externalTests/rayTrace.js
@@ -23,4 +23,34 @@ module.exports = () => async (bot) => {
   block = bot.blockInSight()
   assert.deepStrictEqual(block.position, relBlock.position)
   assert.deepStrictEqual(block.face, relBlock.face)
+
+  // Regression for #3935: a yaw or pitch of exactly 0 is a valid orientation
+  // and must not be rejected by the validation in blockAtEntityCursor.
+  // yaw=0, pitch=0 looks straight ahead along -Z. Build a small stone wall a
+  // couple of blocks ahead at eye level (3 wide, to stay robust to the bot's
+  // exact sub-block position), clear the path in front of it, then assert the
+  // ray trace finds the wall instead of returning null.
+  const pos = bot.entity.position
+  const bx = Math.floor(pos.x)
+  const bz = Math.floor(pos.z)
+  const eyeY = Math.floor(pos.y + bot.entity.height)
+  // clear the eye-level path in front of the bot (2 deep, 3 wide)
+  for (const dz of [0, -1]) {
+    for (const dx of [-1, 0, 1]) {
+      await bot.test.setBlock({ x: bx + dx, y: eyeY, z: bz + dz, blockName: 'air' })
+    }
+  }
+  // stone wall 2 blocks ahead
+  for (const dx of [-1, 0, 1]) {
+    await bot.test.setBlock({ x: bx + dx, y: eyeY, z: bz - 2, blockName: 'stone' })
+  }
+  bot.entity.yaw = 0
+  bot.entity.pitch = 0
+  const zeroBlock = bot.blockAtEntityCursor(bot.entity, 16)
+  assert.ok(zeroBlock, 'blockAtEntityCursor returned null for zero yaw/pitch (#3935)')
+  assert.strictEqual(zeroBlock.name, 'stone')
+  // tidy up the wall
+  for (const dx of [-1, 0, 1]) {
+    await bot.test.setBlock({ x: bx + dx, y: eyeY, z: bz - 2, blockName: 'air' })
+  }
 }