diff --git a/spec/std/big/big_int_spec.cr b/spec/std/big/big_int_spec.cr
index 8a86939efbac..68eba643a571 100644
--- a/spec/std/big/big_int_spec.cr
+++ b/spec/std/big/big_int_spec.cr
@@ -283,6 +283,34 @@ describe "BigInt" do
     -5.to_big_i.remainder(-3).should eq(-2)
   end
 
+  it "#bit" do
+    x = 123.to_big_i
+    x.bit(-10.to_big_i ** 99).should eq(0)
+    x.bit(-(2.to_big_i ** 64)).should eq(0)
+    x.bit(-1).should eq(0)
+    x.bit(0).should eq(1)
+    x.bit(2).should eq(0)
+    x.bit(3).should eq(1)
+    x.bit(6).should eq(1)
+    x.bit(7).should eq(0)
+    x.bit(64).should eq(0)
+    x.bit(2.to_big_i ** 64).should eq(0)
+    x.bit(10.to_big_i ** 99).should eq(0)
+
+    x = ~(123.to_big_i)
+    x.bit(-10.to_big_i ** 99).should eq(0)
+    x.bit(-(2.to_big_i ** 64)).should eq(0)
+    x.bit(-1).should eq(0)
+    x.bit(0).should eq(0)
+    x.bit(2).should eq(1)
+    x.bit(3).should eq(0)
+    x.bit(6).should eq(0)
+    x.bit(7).should eq(1)
+    x.bit(64).should eq(1)
+    x.bit(2.to_big_i ** 64).should eq(1)
+    x.bit(10.to_big_i ** 99).should eq(1)
+  end
+
   it "does bitwise and" do
     (123.to_big_i & 321).should eq(65)
     (BigInt.new("96238761238973286532") & 86325735648).should eq(69124358272)
diff --git a/src/big/big_int.cr b/src/big/big_int.cr
index decf7a0828ff..ad92a1e2cd39 100644
--- a/src/big/big_int.cr
+++ b/src/big/big_int.cr
@@ -385,6 +385,12 @@ struct BigInt < Int
     BigInt.new { |mpz| LibGMP.com(mpz, self) }
   end
 
+  def bit(bit : Int)
+    return 0 if bit < 0
+    return self < 0 ? 1 : 0 if bit > LibGMP::BitcntT::MAX
+    LibGMP.tstbit(self, LibGMP::BitcntT.new!(bit))
+  end
+
   def &(other : Int) : BigInt
     BigInt.new { |mpz| LibGMP.and(mpz, self, other.to_big_i) }
   end
diff --git a/src/big/lib_gmp.cr b/src/big/lib_gmp.cr
index 9caf408f1494..3cae0de64b77 100644
--- a/src/big/lib_gmp.cr
+++ b/src/big/lib_gmp.cr
@@ -116,6 +116,8 @@ lib LibGMP
   fun xor = __gmpz_xor(rop : MPZ*, op1 : MPZ*, op2 : MPZ*)
   fun com = __gmpz_com(rop : MPZ*, op : MPZ*)
 
+  fun tstbit = __gmpz_tstbit(op : MPZ*, bit_index : BitcntT) : Int
+
   fun fdiv_q_2exp = __gmpz_fdiv_q_2exp(q : MPZ*, n : MPZ*, b : BitcntT)
   fun mul_2exp = __gmpz_mul_2exp(rop : MPZ*, op1 : MPZ*, op2 : BitcntT)