diff --git a/src/lib.rs b/src/lib.rs
index 138b752..3a954f3 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -232,12 +232,13 @@ impl NumTraits {
 pub fn from_primitive(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = if let Some(inner_ty) = newtype_inner(&ast.data) {
         quote! {
-            impl #import::FromPrimitive for #name {
+            impl #impl_ #import::FromPrimitive for #name #type_ #where_ #inner_ty: #import::FromPrimitive {
                 fn from_i64(n: i64) -> Option<Self> {
                     <#inner_ty as #import::FromPrimitive>::from_i64(n).map(#name)
                 }
@@ -320,7 +321,7 @@ pub fn from_primitive(input: TokenStream) -> TokenStream {
         };
 
         quote! {
-            impl #import::FromPrimitive for #name {
+            impl #impl_ #import::FromPrimitive for #name #type_ #where_ {
                 #[allow(trivial_numeric_casts)]
                 fn from_i64(#from_i64_var: i64) -> Option<Self> {
                     #(#clauses else)* {
@@ -390,12 +391,13 @@ pub fn from_primitive(input: TokenStream) -> TokenStream {
 pub fn to_primitive(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = if let Some(inner_ty) = newtype_inner(&ast.data) {
         quote! {
-            impl #import::ToPrimitive for #name {
+            impl #impl_ #import::ToPrimitive for #name #type_ #where_ #inner_ty: #import::ToPrimitive {
                 fn to_i64(&self) -> Option<i64> {
                     <#inner_ty as #import::ToPrimitive>::to_i64(&self.0)
                 }
@@ -481,7 +483,7 @@ pub fn to_primitive(input: TokenStream) -> TokenStream {
         };
 
         quote! {
-            impl #import::ToPrimitive for #name {
+            impl #impl_ #import::ToPrimitive for #name #type_ #where_ {
                 #[allow(trivial_numeric_casts)]
                 fn to_i64(&self) -> Option<i64> {
                     #match_expr
@@ -511,33 +513,34 @@ const NEWTYPE_ONLY: &str = "This trait can only be derived for newtypes";
 pub fn num_ops(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
     let impl_ = quote! {
-        impl ::std::ops::Add for #name {
+        impl #impl_ ::std::ops::Add for #name #type_ #where_ #inner_ty: ::std::ops::Add<Output = #inner_ty> {
             type Output = Self;
             fn add(self, other: Self) -> Self {
                 #name(<#inner_ty as ::std::ops::Add>::add(self.0, other.0))
             }
         }
-        impl ::std::ops::Sub for #name {
+        impl #impl_ ::std::ops::Sub for #name #type_ #where_ #inner_ty: ::std::ops::Sub<Output = #inner_ty> {
             type Output = Self;
             fn sub(self, other: Self) -> Self {
                 #name(<#inner_ty as ::std::ops::Sub>::sub(self.0, other.0))
             }
         }
-        impl ::std::ops::Mul for #name {
+        impl #impl_ ::std::ops::Mul for #name #type_ #where_ #inner_ty: ::std::ops::Mul<Output = #inner_ty> {
             type Output = Self;
             fn mul(self, other: Self) -> Self {
                 #name(<#inner_ty as ::std::ops::Mul>::mul(self.0, other.0))
             }
         }
-        impl ::std::ops::Div for #name {
+        impl #impl_ ::std::ops::Div for #name #type_ #where_ #inner_ty: ::std::ops::Div<Output = #inner_ty> {
             type Output = Self;
             fn div(self, other: Self) -> Self {
                 #name(<#inner_ty as ::std::ops::Div>::div(self.0, other.0))
             }
         }
-        impl ::std::ops::Rem for #name {
+        impl #impl_ ::std::ops::Rem for #name #type_ #where_ #inner_ty: ::std::ops::Rem<Output = #inner_ty> {
             type Output = Self;
             fn rem(self, other: Self) -> Self {
                 #name(<#inner_ty as ::std::ops::Rem>::rem(self.0, other.0))
@@ -555,13 +558,16 @@ pub fn num_ops(input: TokenStream) -> TokenStream {
 pub fn num_cast(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
+    let fn_param = proc_macro2::Ident::new("FROM_T", name.span());
 
     let import = NumTraits::new(&ast);
 
     let impl_ = quote! {
-        impl #import::NumCast for #name {
-            fn from<T: #import::ToPrimitive>(n: T) -> Option<Self> {
+        impl #impl_ #import::NumCast for #name #type_ #where_ #inner_ty: #import::NumCast {
+            #[allow(non_camel_case_types)]
+            fn from<#fn_param: #import::ToPrimitive>(n: #fn_param) -> Option<Self> {
                 <#inner_ty as #import::NumCast>::from(n).map(#name)
             }
         }
@@ -577,12 +583,13 @@ pub fn num_cast(input: TokenStream) -> TokenStream {
 pub fn zero(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = quote! {
-        impl #import::Zero for #name {
+        impl #impl_ #import::Zero for #name #type_ #where_ #inner_ty: #import::Zero {
             fn zero() -> Self {
                 #name(<#inner_ty as #import::Zero>::zero())
             }
@@ -602,12 +609,13 @@ pub fn zero(input: TokenStream) -> TokenStream {
 pub fn one(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = quote! {
-        impl #import::One for #name {
+        impl #impl_ #import::One for #name #type_ #where_ #inner_ty: #import::One + PartialEq {
             fn one() -> Self {
                 #name(<#inner_ty as #import::One>::one())
             }
@@ -620,6 +628,17 @@ pub fn one(input: TokenStream) -> TokenStream {
     import.wrap("One", &name, impl_).into()
 }
 
+fn split_for_impl(
+    generics: &syn::Generics,
+) -> (syn::ImplGenerics, syn::TypeGenerics, impl quote::ToTokens) {
+    let (impl_, type_, where_) = generics.split_for_impl();
+    let where_ = match where_ {
+        Some(where_) => quote! { #where_, },
+        None => quote! { where },
+    };
+    (impl_, type_, where_)
+}
+
 /// Derives [`num_traits::Num`][num] for newtypes.  The inner type must already implement `Num`.
 ///
 /// [num]: https://docs.rs/num-traits/0.2/num_traits/trait.Num.html
@@ -627,12 +646,13 @@ pub fn one(input: TokenStream) -> TokenStream {
 pub fn num(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = quote! {
-        impl #import::Num for #name {
+        impl #impl_ #import::Num for #name #type_ #where_ #inner_ty: #import::Num {
             type FromStrRadixErr = <#inner_ty as #import::Num>::FromStrRadixErr;
             fn from_str_radix(s: &str, radix: u32) -> Result<Self, Self::FromStrRadixErr> {
                 <#inner_ty as #import::Num>::from_str_radix(s, radix).map(#name)
@@ -651,12 +671,13 @@ pub fn num(input: TokenStream) -> TokenStream {
 pub fn float(input: TokenStream) -> TokenStream {
     let ast: syn::DeriveInput = syn::parse(input).unwrap();
     let name = &ast.ident;
+    let (impl_, type_, where_) = split_for_impl(&ast.generics);
     let inner_ty = newtype_inner(&ast.data).expect(NEWTYPE_ONLY);
 
     let import = NumTraits::new(&ast);
 
     let impl_ = quote! {
-        impl #import::Float for #name {
+        impl #impl_ #import::Float for #name #type_ #where_ #inner_ty: #import::Float {
             fn nan() -> Self {
                 #name(<#inner_ty as #import::Float>::nan())
             }
diff --git a/tests/generic_newtype.rs b/tests/generic_newtype.rs
new file mode 100644
index 0000000..725f14f
--- /dev/null
+++ b/tests/generic_newtype.rs
@@ -0,0 +1,97 @@
+extern crate num as num_renamed;
+#[macro_use]
+extern crate num_derive;
+
+use crate::num_renamed::{Float, FromPrimitive, Num, NumCast, One, ToPrimitive, Zero};
+use std::ops::Neg;
+
+#[derive(
+    Debug,
+    Clone,
+    Copy,
+    PartialEq,
+    PartialOrd,
+    ToPrimitive,
+    FromPrimitive,
+    NumOps,
+    NumCast,
+    One,
+    Zero,
+    Num,
+    Float,
+)]
+struct MyThing<T: Cake>(T)
+where
+    T: Lie;
+
+trait Cake {}
+trait Lie {}
+
+impl Cake for f32 {}
+impl Lie for f32 {}
+
+impl<T: Neg<Output = T> + Cake + Lie> Neg for MyThing<T> {
+    type Output = Self;
+    fn neg(self) -> Self {
+        MyThing(self.0.neg())
+    }
+}
+
+#[test]
+fn test_from_primitive() {
+    assert_eq!(MyThing::from_u32(25), Some(MyThing(25.0)));
+}
+
+#[test]
+fn test_from_primitive_128() {
+    assert_eq!(
+        MyThing::from_i128(std::i128::MIN),
+        Some(MyThing((-2.0).powi(127)))
+    );
+}
+
+#[test]
+fn test_to_primitive() {
+    assert_eq!(MyThing(25.0).to_u32(), Some(25));
+}
+
+#[test]
+fn test_to_primitive_128() {
+    let f: MyThing<f32> = MyThing::from_f32(std::f32::MAX).unwrap();
+    assert_eq!(f.to_i128(), None);
+    assert_eq!(f.to_u128(), Some(0xffff_ff00_0000_0000_0000_0000_0000_0000));
+}
+
+#[test]
+fn test_num_ops() {
+    assert_eq!(MyThing(25.0) + MyThing(10.0), MyThing(35.0));
+    assert_eq!(MyThing(25.0) - MyThing(10.0), MyThing(15.0));
+    assert_eq!(MyThing(25.0) * MyThing(2.0), MyThing(50.0));
+    assert_eq!(MyThing(25.0) / MyThing(10.0), MyThing(2.5));
+    assert_eq!(MyThing(25.0) % MyThing(10.0), MyThing(5.0));
+}
+
+#[test]
+fn test_num_cast() {
+    assert_eq!(<MyThing<f32> as NumCast>::from(25u8), Some(MyThing(25.0)));
+}
+
+#[test]
+fn test_zero() {
+    assert_eq!(MyThing::zero(), MyThing(0.0));
+}
+
+#[test]
+fn test_one() {
+    assert_eq!(MyThing::one(), MyThing(1.0));
+}
+
+#[test]
+fn test_num() {
+    assert_eq!(MyThing::from_str_radix("25", 10).ok(), Some(MyThing(25.0)));
+}
+
+#[test]
+fn test_float() {
+    assert_eq!(MyThing(4.0).log(MyThing(2.0)), MyThing(2.0));
+}