diff --git a/LICENSE b/LICENSE
index e47bad667a..b182efbdc5 100644
--- a/LICENSE
+++ b/LICENSE
@@ -280,6 +280,37 @@ code from actors <https://github.com/plokhotnyuk/actors> which was released unde
 
 ---------------
 
+pekko-actor contains code in `org.apache.pekko.util.FrequencySketch.scala` which was based on
+code from hash-prospector <https://github.com/skeeto/hash-prospector> which has been placed
+in the public domain.
+
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org/>
+
+---------------
+
 pekko-cluster contains VectorClock.scala which is derived from code written
 by Coda Hale <https://github.com/codahale/vlock>.
 He has agreed to allow us to use this code under an Apache 2.0 license
diff --git a/actor/src/main/scala/org/apache/pekko/util/FrequencySketch.scala b/actor/src/main/scala/org/apache/pekko/util/FrequencySketch.scala
index d328ba8e9f..84cb7e5edd 100644
--- a/actor/src/main/scala/org/apache/pekko/util/FrequencySketch.scala
+++ b/actor/src/main/scala/org/apache/pekko/util/FrequencySketch.scala
@@ -308,6 +308,7 @@ private[pekko] final class FastFrequencySketch[A](width: Int, resetSize: Int) {
 
   // A low-bias hash function found by Hash Function Prospector
   // https://github.com/skeeto/hash-prospector
+  // hash-prospector has been placed in public domain - https://github.com/skeeto/hash-prospector/blob/master/UNLICENSE
   private def rehash(hash: Int): Int = {
     var x = hash
     x = ((x >>> 15) ^ x) * 0xD168AAAD
diff --git a/legal/pekko-actor-jar-license.txt b/legal/pekko-actor-jar-license.txt
index 7d2419e6d3..6079a23779 100644
--- a/legal/pekko-actor-jar-license.txt
+++ b/legal/pekko-actor-jar-license.txt
@@ -277,3 +277,34 @@ be interpreted as representing official policies, either expressed or implied, o
 
 pekko-actor contains code in `org.apache.pekko.dispatch.AbstractBoundedNodeQueue.java` which was based on
 code from actors <https://github.com/plokhotnyuk/actors> which was released under the Apache 2.0 license.
+
+---------------
+
+pekko-actor contains code in `org.apache.pekko.util.FrequencySketch.scala` which was based on
+code from hash-prospector <https://github.com/skeeto/hash-prospector> which has been placed
+in the public domain.
+
+This is free and unencumbered software released into the public domain.
+
+Anyone is free to copy, modify, publish, use, compile, sell, or
+distribute this software, either in source code form or as a compiled
+binary, for any purpose, commercial or non-commercial, and by any
+means.
+
+In jurisdictions that recognize copyright laws, the author or authors
+of this software dedicate any and all copyright interest in the
+software to the public domain. We make this dedication for the benefit
+of the public at large and to the detriment of our heirs and
+successors. We intend this dedication to be an overt act of
+relinquishment in perpetuity of all present and future rights to this
+software under copyright law.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
+EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
+MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.
+IN NO EVENT SHALL THE AUTHORS BE LIABLE FOR ANY CLAIM, DAMAGES OR
+OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
+ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
+OTHER DEALINGS IN THE SOFTWARE.
+
+For more information, please refer to <http://unlicense.org/>