diff --git a/src/readthrd.c b/src/readthrd.c
index 13d64e1..d167701 100644
--- a/src/readthrd.c
+++ b/src/readthrd.c
@@ -180,10 +180,17 @@ static ssize_t check_file(const char *f)
     return ret;
 }
 
-
 static int next_power_of_2(int x)
 {
-    return (x & -x) + x;
+    x--;
+    x |= x >> 1;
+    x |= x >> 2;
+    x |= x >> 4;
+    x |= x >> 8;
+    x |= x >> 16;
+    x++;
+
+   return x;
 }
 
 struct readthrd *readthrd_start(const char *fpath,
diff --git a/src/writethrd.c b/src/writethrd.c
index 2f5c147..ab7b6c2 100644
--- a/src/writethrd.c
+++ b/src/writethrd.c
@@ -200,7 +200,15 @@ static int check_file(const char *f, int truncate)
 
 static int next_power_of_2(int x)
 {
-    return (x & -x) + x;
+    x--;
+    x |= x >> 1;
+    x |= x >> 2;
+    x |= x >> 4;
+    x |= x >> 8;
+    x |= x >> 16;
+    x++;
+
+   return x;
 }
 
 struct writethrd *writethrd_start(const char *fpath, const char *swap_phrase,