diff --git a/include/internal/catch_approx.cpp b/include/internal/catch_approx.cpp
index ca3ac94a..826a1049 100644
--- a/include/internal/catch_approx.cpp
+++ b/include/internal/catch_approx.cpp
@@ -23,7 +23,7 @@ namespace Detail {
     Approx::Approx ( double value )
     :   m_epsilon( std::numeric_limits<float>::epsilon()*100 ),
         m_margin( 0.0 ),
-        m_scale( 1.0 ),
+        m_scale( 0.0 ),
         m_value( value )
     {}
 
diff --git a/include/internal/catch_approx.h b/include/internal/catch_approx.h
index 69428c8a..8ca7f315 100644
--- a/include/internal/catch_approx.h
+++ b/include/internal/catch_approx.h
@@ -44,8 +44,9 @@ namespace Detail {
         friend bool operator == ( const T& lhs, Approx const& rhs ) {
             // Thanks to Richard Harris for his help refining this formula
             auto lhs_v = static_cast<double>(lhs);
-            bool relativeOK = std::fabs(lhs_v - rhs.m_value) < rhs.m_epsilon * (rhs.m_scale +
-                    dmax(std::fabs(lhs_v), std::fabs(rhs.m_value)));
+
+            bool relativeOK = std::fabs( lhs_v - rhs.m_value ) < rhs.m_epsilon * (rhs.m_scale + std::fabs(rhs.m_value) );
+
             if (relativeOK) {
                 return true;
             }
@@ -89,7 +90,11 @@ namespace Detail {
 
         template <typename T, typename = typename std::enable_if<std::is_constructible<double, T>::value>::type>
         Approx& epsilon( T const& newEpsilon ) {
-            m_epsilon = static_cast<double>(newEpsilon);
+            double asDouble = static_cast<double>(newEpsilon);
+            CATCH_ENFORCE(asDouble >= 0 && asDouble <= 1.0,
+                          "Invalid Approx::epsilon: " << m_epsilon <<
+                          ", Approx::epsilon has to be between 0 and 1");
+            m_epsilon = asDouble;
             return *this;
         }