diff --git a/build.tk b/build.tk
index abf1300c..be470037 100644
--- a/build.tk
+++ b/build.tk
@@ -432,14 +432,14 @@ proc CreateCustomH {} {
     while {[gets $in line] != -1} {
 	switch -glob -- $line {
 	    "#define DEFAULT_LATITUDE *" {
-                set $lat [expr $LAT_DEG + ($LAT_MIN/60) + ($LAT_SEC/3600)]
+                set lat [expr $LAT_DEG + ($LAT_MIN/60.0)];
 		puts $out "#define DEFAULT_LATITUDE $lat"
 		.msgs insert end "#define DEFAULT_LATITUDE $lat"
 	    }
 	    "#define DEFAULT_LONGITUDE *" {
-                set $lon [expr -1 * ($LAT_DEG + ($LAT_MIN/60) + ($LAT_SEC/3600))]
-		puts $out "#define DEFAULT_LONGITUDE $lat"
-		.msgs insert end "#define DEFAULT_LONGITUDE $lat"
+                set lon [expr -1.0 * ($LON_DEG + ($LON_MIN/60.0))]
+		puts $out "#define DEFAULT_LONGITUDE $lon"
+		.msgs insert end "#define DEFAULT_LONGITUDE $lon"
 	    }
 	    "#define LOCATION *" {
 		puts $out "#define LOCATION \"$Config(LOCATION)\""