diff --git a/cmake/CompilerOptions.cmake b/cmake/CompilerOptions.cmake
index e5447d88e7d0009f8ec697bb1463e3a7b737b0d8..167ae04818f6c2eb791704de08d7bd99adb449fb 100644
--- a/cmake/CompilerOptions.cmake
+++ b/cmake/CompilerOptions.cmake
@@ -12,3 +12,11 @@ if(${CMAKE_CXX_COMPILER_ID} MATCHES "Clang")
 
     set(CXXOPT_WALL "${CXXOPT_WALL} -Wno-missing-braces")
 endif()
+
+if(${CMAKE_CXX_COMPILER_ID} MATCHES "Intel")
+    # Disable warning for unused template parameter
+    # this is raised by a templated function in the json library
+
+    set(CXXOPT_WALL "${CXXOPT_WALL} -wd488")
+endif()
+
diff --git a/src/util/optional.hpp b/src/util/optional.hpp
index 0d71c4a5d564b4a85db457a930f803388ee0861b..0955ea99e720a24e1a02ea4926a838caec8ee2d7 100644
--- a/src/util/optional.hpp
+++ b/src/util/optional.hpp
@@ -332,7 +332,12 @@ struct optional<X&>: detail::optional_base<X&> {
     template <typename T>
     optional(optional<T&>& ot): base(ot.set,ot.ref()) {}
 
-    template <typename Y,typename = typename std::enable_if<!detail::is_optional<Y>()>::type>
+    /*
+    template <
+        typename Y,
+        typename = typename std::enable_if<!detail::is_optional<Y>::value>::type>
+    */
+    template <typename Y>
     optional& operator=(Y& y) {
         set = true;
         ref() = y;
@@ -363,7 +368,7 @@ struct optional<void>: detail::optional_base<void> {
 
     template <typename T>
     optional(const optional<T>& o): base(o.set,true) {}
-    
+
     template <typename T>
     optional& operator=(T) {
         set = true;
diff --git a/tests/test_optional.cpp b/tests/test_optional.cpp
index 9c6f35cfa658ab1c45cee53250eaa747d89dea25..aa13e870d205c19bf2e9a26b9f03b03eaeef866f 100644
--- a/tests/test_optional.cpp
+++ b/tests/test_optional.cpp
@@ -53,7 +53,7 @@ TEST(optionalm,deref) {
         explicit foo(int a_): a(a_) {}
         double value() { return 3.0*a; }
     };
-    
+
     optional<foo> f=foo(2);
     EXPECT_EQ(6.0,f->value());
     EXPECT_EQ(2,(*f).a);
@@ -88,22 +88,20 @@ TEST(optionalm,assign_returns) {
     EXPECT_EQ(&a,bp);
 }
 
-namespace {
-    struct nomove {
-        int value;
+struct nomove {
+    int value;
 
-        nomove(): value(0) {}
-        nomove(int i): value(i) {}
-        nomove(const nomove &n): value(n.value) {}
-        nomove(nomove &&n) = delete;
+    nomove(): value(0) {}
+    nomove(int i): value(i) {}
+    nomove(const nomove &n): value(n.value) {}
+    nomove(nomove &&n) = delete;
 
-        nomove &operator=(const nomove &n) { value=n.value; return *this; }
+    nomove &operator=(const nomove &n) { value=n.value; return *this; }
+
+    bool operator==(const nomove &them) const { return them.value==value; }
+    bool operator!=(const nomove &them) const { return !(*this==them); }
+};
 
-        bool operator==(const nomove &them) const { return them.value==value; }
-        bool operator!=(const nomove &them) const { return !(*this==them); }
-    };
-}
- 
 TEST(optionalm,ctor_nomove) {
     optional<nomove> a(nomove(3));
     EXPECT_EQ(nomove(3),a.get());
@@ -116,30 +114,28 @@ TEST(optionalm,ctor_nomove) {
     EXPECT_EQ(nomove(4),b.get());
 }
 
-namespace {
-    struct nocopy {
-        int value;
-
-        nocopy(): value(0) {}
-        nocopy(int i): value(i) {}
-        nocopy(const nocopy &n) = delete;
-        nocopy(nocopy &&n) {
-            value=n.value;
-            n.value=0;
-        }
-
-        nocopy &operator=(const nocopy &n) = delete;
-        nocopy &operator=(nocopy &&n) {
-            value=n.value;
-            n.value=-1;
-            return *this;
-        }
-
-        bool operator==(const nocopy &them) const { return them.value==value; }
-        bool operator!=(const nocopy &them) const { return !(*this==them); }
-    };
-}
-    
+struct nocopy {
+    int value;
+
+    nocopy(): value(0) {}
+    nocopy(int i): value(i) {}
+    nocopy(const nocopy &n) = delete;
+    nocopy(nocopy &&n) {
+        value=n.value;
+        n.value=0;
+    }
+
+    nocopy &operator=(const nocopy &n) = delete;
+    nocopy &operator=(nocopy &&n) {
+        value=n.value;
+        n.value=-1;
+        return *this;
+    }
+
+    bool operator==(const nocopy &them) const { return them.value==value; }
+    bool operator!=(const nocopy &them) const { return !(*this==them); }
+};
+
 TEST(optionalm,ctor_nocopy) {
     optional<nocopy> a(nocopy(5));
     EXPECT_EQ(nocopy(5),a.get());
@@ -152,12 +148,10 @@ TEST(optionalm,ctor_nocopy) {
     EXPECT_EQ(nocopy(6),b.get());
 }
 
-namespace {
-    optional<double> odd_half(int n) {
-        optional<double> h;
-        if (n%2==1) h=n/2.0;
-        return h;
-    }
+optional<double> odd_half(int n) {
+    optional<double> h;
+    if (n%2==1) h=n/2.0;
+    return h;
 }
 
 TEST(optionalm,bind) {
@@ -199,7 +193,7 @@ TEST(optionalm,void) {
 
 TEST(optionalm,bind_to_void) {
     optional<int> a,b(3);
-    
+
     int call_count=0;
     auto vf=[&call_count](int i) -> void { ++call_count; };
 
@@ -213,12 +207,14 @@ TEST(optionalm,bind_to_void) {
     EXPECT_TRUE((bool)x);
     EXPECT_EQ(1,call_count);
 }
-    
+
 TEST(optionalm,bind_to_optional_void) {
     optional<int> a,b(3),c(4);
-    
+
     int count=0;
-    auto count_if_odd=[&count](int i) { return i%2?(++count,optional<void>(true)):optional<void>(); };
+    auto count_if_odd=[&count](int i) {
+        return i%2?(++count,optional<void>(true)):optional<void>();
+    };
 
     auto x=a >> count_if_odd;
     EXPECT_EQ(typeid(optional<void>),typeid(x));
@@ -242,12 +238,10 @@ TEST(optionalm,bind_with_ref) {
     EXPECT_EQ(11,*a);
 }
 
-namespace {
-    struct check_cref {
-        int operator()(const int &) { return 10; }
-        int operator()(int &) { return 11; }
-    };
-}
+struct check_cref {
+    int operator()(const int &) { return 10; }
+    int operator()(int &) { return 11; }
+};
 
 TEST(optionalm,bind_constness) {
     check_cref checker;
@@ -314,7 +308,7 @@ TEST(optionalm,and_operator) {
     auto zb=false & b;
     EXPECT_EQ(typeid(zb),typeid(b));
     EXPECT_FALSE((bool)zb);
-    
+
     auto b3=b & 3;
     EXPECT_EQ(typeid(b3),typeid(optional<int>));
     EXPECT_TRUE((bool)b3);