diff --git a/src/devices/machine/fdc_pll.cpp b/src/devices/machine/fdc_pll.cpp
index 3f54f0b0c2e..d384842fe3d 100644
--- a/src/devices/machine/fdc_pll.cpp
+++ b/src/devices/machine/fdc_pll.cpp
@@ -17,9 +17,10 @@ std::string fdc_pll_t::tts(attotime t)
 void fdc_pll_t::set_clock(const attotime &_period)
 {
 	period = _period;
-	period_adjust_base = period * 0.05;
-	min_period = period * 0.75;
-	max_period = period * 1.25;
+	double period_as_double = period.as_double();
+	period_adjust_base = attotime::from_double(period_as_double * 0.05);
+	min_period = attotime::from_double(period_as_double * 0.75);
+	max_period = attotime::from_double(period_as_double * 1.25);
 }
 
 void fdc_pll_t::reset(const attotime &when)