diff --git a/DESCRIPTION b/DESCRIPTION
index 2395e651..efc83a4c 100644
--- a/DESCRIPTION
+++ b/DESCRIPTION
@@ -1,5 +1,5 @@
 Package: parallelly
-Version: 1.40.1-9006
+Version: 1.40.1-9007
 Title: Enhancing the 'parallel' Package
 Imports:
     parallel,
diff --git a/NEWS.md b/NEWS.md
index 26c6c544..66b81d7e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -8,6 +8,12 @@
  * `makeClusterPSOCK()` will now produce an error, rather than a
    warning, when the local system command used to launch the parallel
    worker failed with a non-zero exit code.
+   
+ * Now `serializedSize()` always returns a double. Previously, it
+   would return an integer, if the value could be represented by an
+   integer. However, it turned out that returning an integer increased
+   the risk for integer overflow later on if, say, to such values were
+   added together.
  
 ## Bug Fixes
 
diff --git a/R/serializedSize.R b/R/serializedSize.R
index 291f28d8..a018f6f2 100644
--- a/R/serializedSize.R
+++ b/R/serializedSize.R
@@ -5,7 +5,7 @@
 #'
 #' @param obj An R object.
 #'
-#' @return (integer or double) Number of bytes needed to serialize this object.
+#' @return (double) Number of bytes needed to serialize this object.
 #'
 #' @examples
 #' object.size(mtcars)
diff --git a/man/serializedSize.Rd b/man/serializedSize.Rd
index cc8701d3..5cd3a382 100644
--- a/man/serializedSize.Rd
+++ b/man/serializedSize.Rd
@@ -10,7 +10,7 @@ serializedSize(obj)
 \item{obj}{An R object.}
 }
 \value{
-(integer or double) Number of bytes needed to serialize this object.
+(double) Number of bytes needed to serialize this object.
 }
 \description{
 This function goes through all the motions of serializing an object, but
diff --git a/src/calc-serialized-size.c b/src/calc-serialized-size.c
index 21083545..4e55e26e 100644
--- a/src/calc-serialized-size.c
+++ b/src/calc-serialized-size.c
@@ -71,9 +71,5 @@ R_xlen_t calc_serialized_size(SEXP robj) {
 //~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
 SEXP R_calc_serialized_size(SEXP robj) {
   R_xlen_t count = calc_serialized_size(robj);
-  if (count > R_INT_MAX) {
-    return(ScalarReal((double) count));
-  } else {
-    return(ScalarInteger(count));
-  }
+  return(ScalarReal((double) count));
 }