diff --git a/src/emucore/TIASurface.cxx b/src/emucore/TIASurface.cxx
index bf3bd7336..7674e3400 100644
--- a/src/emucore/TIASurface.cxx
+++ b/src/emucore/TIASurface.cxx
@@ -32,7 +32,7 @@ TIASurface::TIASurface(OSystem& system)
     myTIA(nullptr),
     myFilterType(kNormal),
     myUsePhosphor(false),
-    myPhosphorPercent(0.77),
+    myPhosphorPercent(0.77f),
     myScanlinesEnabled(false),
     myPalette(nullptr)
 {
diff --git a/src/emucore/TIASurface.hxx b/src/emucore/TIASurface.hxx
index 39484eb6b..41cf1998c 100644
--- a/src/emucore/TIASurface.hxx
+++ b/src/emucore/TIASurface.hxx
@@ -120,7 +120,7 @@ class TIASurface
     */
     uInt8 getPhosphor(uInt8 c1, uInt8 c2) const {
       // Use maximum of current and decayed previous values
-      c2 *= myPhosphorPercent;
+      c2 = uInt8(c2 * myPhosphorPercent);
       if(c1 > c2)  return c1; // raise (assumed immediate)
       else         return c2; // decay
     }