diff --git a/src/jtag/startup.tcl b/src/jtag/startup.tcl
index 6f9c000d8..f88ef1fa4 100644
--- a/src/jtag/startup.tcl
+++ b/src/jtag/startup.tcl
@@ -81,8 +81,9 @@ proc srst_asserted {} {
 # measure actual JTAG clock
 proc measure_clk {} {
 	set start_time [ms];
-	runtest 10000000; 
-	echo "Running at more than [expr 10000.0 / ([ms]-$start_time)] kHz";
+        set iterations 10000000;
+	runtest $iterations;
+	echo "Running at more than [expr $iterations.0 / ([ms]-$start_time)] kHz";
 }
 
 add_help_text measure_clk "Runs a test to measure the JTAG clk. Useful with RCLK / RTCK."