diff --git a/doc/misc/calc.texi b/doc/misc/calc.texi
index baf46f71703..7bd060189c5 100644
--- a/doc/misc/calc.texi
+++ b/doc/misc/calc.texi
@@ -19111,8 +19111,8 @@ the operation is left in symbolic form.
 @tindex lcm
 The @kbd{k l} (@code{calc-lcm}) [@code{lcm}] command computes the
 Least Common Multiple of two integers or fractions.  The product of
-the LCM and GCD of two numbers is equal to the product of the
-numbers.
+the LCM and GCD of two numbers is equal to the absolute value of the
+product of the numbers.
 
 @kindex k E
 @pindex calc-extended-gcd
diff --git a/lisp/calc/calc-comb.el b/lisp/calc/calc-comb.el
index bc1ac315a01..c84ff236851 100644
--- a/lisp/calc/calc-comb.el
+++ b/lisp/calc/calc-comb.el
@@ -260,7 +260,7 @@
 (defun calcFunc-lcm (a b)
   (let ((g (calcFunc-gcd a b)))
     (if (Math-numberp g)
-	(math-div (math-mul a b) g)
+	(math-div (math-abs (math-mul a b)) g)
       (list 'calcFunc-lcm a b))))
 
 (defun calcFunc-egcd (a b)   ; Knuth section 4.5.2