diff --git a/lib/init-7.scm b/lib/init-7.scm
index b2147437..bf8a7b19 100644
--- a/lib/init-7.scm
+++ b/lib/init-7.scm
@@ -1039,13 +1039,6 @@
 
 (define (eqv? a b) (if (eq? a b) #t (and (number? a) (equal? a b))))
 
-(define (exact-integer-sqrt x)
-  (let ((res (sqrt x)))
-    (if (exact? res)
-        (values res 0)
-        (let ((res (inexact->exact (truncate res))))
-          (values res (- x (* res res)))))))
-
 (define (zero? x) (= x 0))
 (define (positive? x) (> x 0))
 (define (negative? x) (< x 0))
diff --git a/lib/scheme/extras.scm b/lib/scheme/extras.scm
index 95f78025..d7f70393 100644
--- a/lib/scheme/extras.scm
+++ b/lib/scheme/extras.scm
@@ -54,6 +54,16 @@
 (define (floor/ n m)
   (values (floor-quotient n m) (floor-remainder n m)))
 
+(define (exact-integer-sqrt x)
+  (let ((res (sqrt x)))
+    (if (exact? res)
+        (values res 0)
+        (let lp ((res (inexact->exact (truncate res))))
+          (let ((rem (- x (* res res))))
+            (if (negative? rem)
+                (lp (- res 1))
+                (values res rem)))))))
+
 ;; Adapted from Bawden's algorithm.
 (define (rationalize x e)
   (define (sr x y return)