diff --git a/inst/include/Rcpp/sugar/functions/max.h b/inst/include/Rcpp/sugar/functions/max.h
index 41d5de539..f366f35c7 100644
--- a/inst/include/Rcpp/sugar/functions/max.h
+++ b/inst/include/Rcpp/sugar/functions/max.h
@@ -32,22 +32,22 @@ namespace sugar{
 
         Max( const T& obj_) : obj(obj_) {}
 
-        operator STORAGE() {
-            max_ = obj[0] ;
-            if( Rcpp::traits::is_na<RTYPE>( max_ ) ) return max_ ;
+        operator STORAGE() const {
+            STORAGE max, current ;
+            max = obj[0] ;
+            if( Rcpp::traits::is_na<RTYPE>( max ) ) return max ;
 
             R_xlen_t n = obj.size() ;
             for( R_xlen_t i=1; i<n; i++){
                 current = obj[i] ;
                 if( Rcpp::traits::is_na<RTYPE>( current ) ) return current;
-                if( current > max_ ) max_ = current ;
+                if( current > max ) max = current ;
             }
-            return max_ ;
+            return max ;
         }
 
     private:
         const T& obj ;
-        STORAGE min_, max_, current ;
     } ;
 
     // version for NA = false
@@ -58,20 +58,20 @@ namespace sugar{
 
         Max( const T& obj_) : obj(obj_) {}
 
-        operator STORAGE() {
-            max_ = obj[0] ;
+        operator STORAGE() const {
+            STORAGE max, current ;
+            max = obj[0] ;
 
             R_xlen_t n = obj.size() ;
             for( R_xlen_t i=1; i<n; i++){
                 current = obj[i] ;
-                if( current > max_ ) max_ = current ;
+                if( current > max ) max = current ;
             }
-            return max_ ;
+            return max ;
         }
 
     private:
         const T& obj ;
-        STORAGE max_, current ;
     } ;
 
 
diff --git a/inst/include/Rcpp/sugar/functions/min.h b/inst/include/Rcpp/sugar/functions/min.h
index 0dd8c2c29..19f577f24 100644
--- a/inst/include/Rcpp/sugar/functions/min.h
+++ b/inst/include/Rcpp/sugar/functions/min.h
@@ -32,21 +32,21 @@ namespace sugar{
 
         Min( const T& obj_) : obj(obj_) {}
 
-        operator STORAGE() {
-            min_ = obj[0] ;
-            if( Rcpp::traits::is_na<RTYPE>( min_ ) ) return min_ ;
+        operator STORAGE() const {
+            STORAGE min, current ;
+            min = obj[0] ;
+            if( Rcpp::traits::is_na<RTYPE>( min ) ) return min ;
 
             R_xlen_t n = obj.size() ;
             for( R_xlen_t i=1; i<n; i++){
                 current = obj[i] ;
                 if( Rcpp::traits::is_na<RTYPE>( current ) ) return current;
-                if( current < min_ ) min_ = current ;
+                if( current < min ) min = current ;
             }
-            return min_ ;
+            return min ;
         }
 
         const T& obj ;
-        STORAGE min_, max_, current ;
     } ;
 
     // version for NA = false
@@ -57,19 +57,19 @@ namespace sugar{
 
         Min( const T& obj_) : obj(obj_) {}
 
-        operator STORAGE() {
-            min_ = obj[0] ;
+        operator STORAGE() const {
+            STORAGE min, current ;
+            min = obj[0] ;
 
             R_xlen_t n = obj.size() ;
             for( R_xlen_t i=1; i<n; i++){
                 current = obj[i] ;
-                if( current < min_ ) min_ = current ;
+                if( current < min ) min = current ;
             }
-            return min_ ;
+            return min ;
         }
 
         const T& obj ;
-        STORAGE min_, current ;
     } ;