diff --git a/jl/bigint.jl b/jl/bigint.jl
index 04b4ff1cd6309..609dec323d312 100644
--- a/jl/bigint.jl
+++ b/jl/bigint.jl
@@ -86,6 +86,12 @@ function cmp(x::BigInt, y::BigInt)
 	ccall(dlsym(_jl_libgmp_wrapper, :_jl_mpz_cmp), Int, (Ptr{Void}, Ptr{Void}),x.mpz, y.mpz)
 end
 
+function sqrt(x::BigInt)
+	z = _jl_bigint_init()
+	ccall(dlsym(_jl_libgmp_wrapper, :_jl_mpz_sqrt), Void, (Ptr{Void}, Ptr{Void}),z,x.mpz)
+	BigInt(z)
+end
+
 ==(x::BigInt, y::BigInt) = cmp(x,y) == 0 
 <=(x::BigInt, y::BigInt) = cmp(x,y) <= 0 
 >=(x::BigInt, y::BigInt) = cmp(x,y) >= 0