diff --git a/TODO.FACTOR.txt b/TODO.FACTOR.txt
index 55d4c33191..30814646ff 100644
--- a/TODO.FACTOR.txt
+++ b/TODO.FACTOR.txt
@@ -2,7 +2,7 @@
 
 - inline float allocation needs a gc check
 - docs: don't pass volatile aliens to callbacks
-- windows rollover broken again
+- some instability remains
 
 + ui:
 
@@ -52,12 +52,10 @@
 - arm backend
 - mac intel: struct returns from objc methods
 - float= doesn't consider nans equal
-- intrinsic fixnum>float float>fixnum
 - C functions returning structs by value
 - infer which variables are read, written in a quotation
 - compiled continuations
 - compiled call traces
-- amd64 structs-by-value bug
 
 + prettyprinter:
 
diff --git a/vm/math.c b/vm/math.c
index b43be01d16..d2825f93ec 100644
--- a/vm/math.c
+++ b/vm/math.c
@@ -473,31 +473,31 @@ void primitive_float_to_str(void)
 void primitive_float_add(void)
 {
 	POP_FLOATS(x,y);
-	box_float(x + y);
+	box_double(x + y);
 }
 
 void primitive_float_subtract(void)
 {
 	POP_FLOATS(x,y);
-	box_float(x - y);
+	box_double(x - y);
 }
 
 void primitive_float_multiply(void)
 {
 	POP_FLOATS(x,y);
-	box_float(x * y);
+	box_double(x * y);
 }
 
 void primitive_float_divfloat(void)
 {
 	POP_FLOATS(x,y);
-	box_float(x / y);
+	box_double(x / y);
 }
 
 void primitive_float_mod(void)
 {
 	POP_FLOATS(x,y);
-	box_float(fmod(x,y));
+	box_double(fmod(x,y));
 }
 
 void primitive_float_less(void)