diff --git a/src/commands.c b/src/commands.c
index 5ee012c79..b9b4b915d 100644
--- a/src/commands.c
+++ b/src/commands.c
@@ -2608,7 +2608,7 @@ struct redisCommandArg PFDEBUG_Args[] = {
 /* PFMERGE argument table */
 struct redisCommandArg PFMERGE_Args[] = {
 {"destkey",ARG_TYPE_KEY,0,NULL,NULL,NULL,CMD_ARG_NONE},
-{"sourcekey",ARG_TYPE_KEY,1,NULL,NULL,NULL,CMD_ARG_MULTIPLE},
+{"sourcekey",ARG_TYPE_KEY,1,NULL,NULL,NULL,CMD_ARG_OPTIONAL|CMD_ARG_MULTIPLE},
 {0}
 };
 
diff --git a/src/commands/pfmerge.json b/src/commands/pfmerge.json
index ae18dad1e..648a8b43a 100644
--- a/src/commands/pfmerge.json
+++ b/src/commands/pfmerge.json
@@ -62,6 +62,7 @@
                 "name": "sourcekey",
                 "type": "key",
                 "key_spec_index": 1,
+                "optional": true,
                 "multiple": true
             }
         ]
diff --git a/src/help.h b/src/help.h
index a95da3695..e8a94210e 100644
--- a/src/help.h
+++ b/src/help.h
@@ -1125,7 +1125,7 @@ struct commandHelp {
     11,
     "2.8.9" },
     { "PFMERGE",
-    "destkey sourcekey [sourcekey ...]",
+    "destkey [sourcekey [sourcekey ...]]",
     "Merge N different HyperLogLogs into a single one.",
     11,
     "2.8.9" },
diff --git a/tests/unit/hyperloglog.tcl b/tests/unit/hyperloglog.tcl
index ed09dacce..0103b2ab9 100644
--- a/tests/unit/hyperloglog.tcl
+++ b/tests/unit/hyperloglog.tcl
@@ -165,6 +165,33 @@ start_server {tags {"hll"}} {
         r pfcount hll{t}
     } {5}
 
+    test {PFMERGE on missing source keys will create an empty destkey} {
+        r del sourcekey{t} sourcekey2{t} destkey{t} destkey2{t}
+
+        assert_equal {OK} [r pfmerge destkey{t} sourcekey{t}]
+        assert_equal 1 [r exists destkey{t}]
+        assert_equal 0 [r pfcount destkey{t}]
+
+        assert_equal {OK} [r pfmerge destkey2{t} sourcekey{t} sourcekey2{t}]
+        assert_equal 1 [r exists destkey2{t}]
+        assert_equal 0 [r pfcount destkey{t}]
+    }
+
+    test {PFMERGE with one empty input key, create an empty destkey} {
+        r del destkey
+        assert_equal {OK} [r pfmerge destkey]
+        assert_equal 1 [r exists destkey]
+        assert_equal 0 [r pfcount destkey]
+    }
+
+    test {PFMERGE with one non-empty input key, dest key is actually one of the source keys} {
+        r del destkey
+        assert_equal 1 [r pfadd destkey a b c]
+        assert_equal {OK} [r pfmerge destkey]
+        assert_equal 1 [r exists destkey]
+        assert_equal 3 [r pfcount destkey]
+    }
+
     test {PFCOUNT multiple-keys merge returns cardinality of union #1} {
         r del hll1{t} hll2{t} hll3{t}
         for {set x 1} {$x < 10000} {incr x} {