diff --git a/src/main/java/org/apache/commons/math/util/FastMath.java b/src/main/java/org/apache/commons/math/util/FastMath.java
index 123be4a96..5f012fb95 100644
--- a/src/main/java/org/apache/commons/math/util/FastMath.java
+++ b/src/main/java/org/apache/commons/math/util/FastMath.java
@@ -576,19 +576,19 @@ public class FastMath {
     /** Compute the signum of a number.
      * The signum is -1 for negative numbers, +1 for positive numbers and 0 otherwise
      * @param a number on which evaluation is done
-     * @return -1, 0, +1 or NaN depending on sign of a
+     * @return -1.0, -0.0, +0.0, +1.0 or NaN depending on sign of a
      */
     public static double signum(final double a) {
-        return (a < 0.0) ? -1.0 : ((a > 0.0) ? 1.0 : a);
+        return (a < 0.0) ? -1.0 : ((a > 0.0) ? 1.0 : a); // return +0.0/-0.0/NaN depending on a
     }
 
     /** Compute the signum of a number.
      * The signum is -1 for negative numbers, +1 for positive numbers and 0 otherwise
      * @param a number on which evaluation is done
-     * @return -1, 0, +1 or NaN depending on sign of a
+     * @return -1.0, -0.0, +0.0, +1.0 or NaN depending on sign of a
      */
     public static float signum(final float a) {
-        return (a < 0.0f) ? -1.0f : ((a > 0.0f) ? 1.0f : a);
+        return (a < 0.0f) ? -1.0f : ((a > 0.0f) ? 1.0f : a); // return +0.0/-0.0/NaN depending on a
     }
 
     /** Compute next number towards positive infinity.