diff --git a/src/librustc/middle/ty.rs b/src/librustc/middle/ty.rs
index a250c6c298b..fb48fded2a5 100644
--- a/src/librustc/middle/ty.rs
+++ b/src/librustc/middle/ty.rs
@@ -4125,6 +4125,7 @@ pub fn is_binopable(cx: &ctxt, ty: t, op: ast::BinOp) -> bool {
     static opcat_eq: int = 5;
     static opcat_bit: int = 6;
     static opcat_logic: int = 7;
+    static opcat_mod: int = 8;
 
     fn opcat(op: ast::BinOp) -> int {
         match op {
@@ -4132,7 +4133,7 @@ pub fn is_binopable(cx: &ctxt, ty: t, op: ast::BinOp) -> bool {
           ast::BiSub => opcat_sub,
           ast::BiMul => opcat_mult,
           ast::BiDiv => opcat_mult,
-          ast::BiRem => opcat_mult,
+          ast::BiRem => opcat_mod,
           ast::BiAnd => opcat_logic,
           ast::BiOr => opcat_logic,
           ast::BiBitXor => opcat_bit,
@@ -4168,14 +4169,14 @@ pub fn is_binopable(cx: &ctxt, ty: t, op: ast::BinOp) -> bool {
     static f: bool = false;
 
     let tbl = [
-    //           +, -, *, shift, rel, ==, bit, logic
-    /*other*/   [f, f, f, f,     f,   f,  f,   f],
-    /*bool*/    [f, f, f, f,     t,   t,  t,   t],
-    /*char*/    [f, f, f, f,     t,   t,  f,   f],
-    /*int*/     [t, t, t, t,     t,   t,  t,   f],
-    /*float*/   [t, t, t, f,     t,   t,  f,   f],
-    /*bot*/     [t, t, t, t,     t,   t,  t,   t],
-    /*raw ptr*/ [f, f, f, f,     t,   t,  f,   f]];
+    //           +, -, *, shift, rel, ==, bit, logic, mod
+    /*other*/   [f, f, f, f,     f,   f,  f,   f,     f],
+    /*bool*/    [f, f, f, f,     t,   t,  t,   t,     f],
+    /*char*/    [f, f, f, f,     t,   t,  f,   f,     f],
+    /*int*/     [t, t, t, t,     t,   t,  t,   f,     t],
+    /*float*/   [t, t, t, f,     t,   t,  f,   f,     f],
+    /*bot*/     [t, t, t, t,     t,   t,  t,   t,     t],
+    /*raw ptr*/ [f, f, f, f,     t,   t,  f,   f,     f]];
 
     return tbl[tycat(cx, ty) as uint ][opcat(op) as uint];
 }
diff --git a/src/libstd/num/f32.rs b/src/libstd/num/f32.rs
index 7c5fe4ff274..cf457763513 100644
--- a/src/libstd/num/f32.rs
+++ b/src/libstd/num/f32.rs
@@ -41,6 +41,7 @@ mod cmath {
         pub fn frexpf(n: c_float, value: &mut c_int) -> c_float;
         pub fn fmaxf(a: c_float, b: c_float) -> c_float;
         pub fn fminf(a: c_float, b: c_float) -> c_float;
+        pub fn fmodf(a: c_float, b: c_float) -> c_float;
         pub fn nextafterf(x: c_float, y: c_float) -> c_float;
         pub fn hypotf(x: c_float, y: c_float) -> c_float;
         pub fn ldexpf(x: c_float, n: c_int) -> c_float;
@@ -201,7 +202,9 @@ impl Div<f32,f32> for f32 {
 #[cfg(not(test))]
 impl Rem<f32,f32> for f32 {
     #[inline]
-    fn rem(&self, other: &f32) -> f32 { *self % *other }
+    fn rem(&self, other: &f32) -> f32 {
+        unsafe { cmath::fmodf(*self, *other) }
+    }
 }
 
 #[cfg(not(test))]
diff --git a/src/libstd/num/f64.rs b/src/libstd/num/f64.rs
index 69328a5ecdc..4a751988d36 100644
--- a/src/libstd/num/f64.rs
+++ b/src/libstd/num/f64.rs
@@ -40,6 +40,7 @@ mod cmath {
         pub fn fdim(a: c_double, b: c_double) -> c_double;
         pub fn fmax(a: c_double, b: c_double) -> c_double;
         pub fn fmin(a: c_double, b: c_double) -> c_double;
+        pub fn fmod(a: c_double, b: c_double) -> c_double;
         pub fn nextafter(x: c_double, y: c_double) -> c_double;
         pub fn frexp(n: c_double, value: &mut c_int) -> c_double;
         pub fn hypot(x: c_double, y: c_double) -> c_double;
@@ -210,7 +211,9 @@ impl Div<f64,f64> for f64 {
 #[cfg(not(test))]
 impl Rem<f64,f64> for f64 {
     #[inline]
-    fn rem(&self, other: &f64) -> f64 { *self % *other }
+    fn rem(&self, other: &f64) -> f64 {
+        unsafe { cmath::fmod(*self, *other) }
+    }
 }
 #[cfg(not(test))]
 impl Neg<f64> for f64 {