diff --git a/dlib/matrix/matrix_expressions.h b/dlib/matrix/matrix_expressions.h
index 4937e8dca..4442ce258 100644
--- a/dlib/matrix/matrix_expressions.h
+++ b/dlib/matrix/matrix_expressions.h
@@ -256,12 +256,12 @@ namespace dlib
 
         template <typename U>
         bool aliases (
-            const matrix_exp<U>& item
+            const matrix_exp<U>& 
         ) const { return false; }
 
         template <typename U>
         bool destructively_aliases (
-            const matrix_exp<U>& item
+            const matrix_exp<U>& 
         ) const { return false; }
 
         long nr (
diff --git a/dlib/svm/sparse_kernel.h b/dlib/svm/sparse_kernel.h
index 0df4f5f0d..ec37fca22 100644
--- a/dlib/svm/sparse_kernel.h
+++ b/dlib/svm/sparse_kernel.h
@@ -299,16 +299,16 @@ namespace dlib
         typename T
         >
     void serialize (
-        const sparse_linear_kernel<T>& item,
-        std::ostream& out
+        const sparse_linear_kernel<T>& ,
+        std::ostream& 
     ){}
 
     template <
         typename T
         >
     void deserialize (
-        sparse_linear_kernel<T>& item,
-        std::istream& in 
+        sparse_linear_kernel<T>& ,
+        std::istream&  
     ){}
 
 // ----------------------------------------------------------------------------------------
@@ -362,16 +362,16 @@ namespace dlib
         typename T
         >
     void serialize (
-        const sparse_histogram_intersection_kernel<T>& item,
-        std::ostream& out
+        const sparse_histogram_intersection_kernel<T>& ,
+        std::ostream& 
     ){}
 
     template <
         typename T
         >
     void deserialize (
-        sparse_histogram_intersection_kernel<T>& item,
-        std::istream& in 
+        sparse_histogram_intersection_kernel<T>& ,
+        std::istream&  
     ){}
 
 // ----------------------------------------------------------------------------------------