diff --git a/dlib/dnn/cudnn_dlibapi.cpp b/dlib/dnn/cudnn_dlibapi.cpp
index e36f64fdc..5e0537267 100644
--- a/dlib/dnn/cudnn_dlibapi.cpp
+++ b/dlib/dnn/cudnn_dlibapi.cpp
@@ -480,6 +480,7 @@ namespace dlib
             catch(...)
             {
                 clear();
+                throw;
             }
         }
 
@@ -581,7 +582,7 @@ namespace dlib
     // ------------------------------------------------------------------------------------
 
         max_pool::max_pool (
-        ) : handle(nullptr),stride_y(0),stride_x(0)
+        ) : handle(nullptr),window_height(0),window_width(0),stride_y(0),stride_x(0)
         {
         }
 
@@ -598,31 +599,52 @@ namespace dlib
             if (handle)
                 cudnnDestroyPoolingDescriptor((cudnnPoolingDescriptor_t)handle);
             handle = nullptr;
+            window_height = 0;
+            window_width = 0;
             stride_y = 0;
             stride_x = 0;
         }
 
         void max_pool::
         setup(
-            int window_height,
-            int window_width,
+            int window_height_,
+            int window_width_,
             int stride_y_,
             int stride_x_
         )
         {
-            stride_x = stride_x_;
-            stride_y = stride_y_;
-            cudnnPoolingDescriptor_t poolingDesc;
-            CHECK_CUDNN(cudnnCreatePoolingDescriptor(&poolingDesc));
-            handle = poolingDesc;
+            if (window_height == window_height_ &&
+                window_width  == window_width_ &&
+                stride_y == stride_y_ &&
+                stride_x == stride_x_ )
+            {
+                return;
+            }
 
-            CHECK_CUDNN(cudnnSetPooling2dDescriptor(poolingDesc,
-                                              CUDNN_POOLING_MAX,
-                                              window_height,
-                                              window_width,
-                                              0,0, // no padding
-                                              stride_y,
-                                              stride_x));
+            clear();
+            try
+            {
+                window_height = window_height_;
+                window_width = window_width_;
+                stride_x = stride_x_;
+                stride_y = stride_y_;
+                cudnnPoolingDescriptor_t poolingDesc;
+                CHECK_CUDNN(cudnnCreatePoolingDescriptor(&poolingDesc));
+                handle = poolingDesc;
+
+                CHECK_CUDNN(cudnnSetPooling2dDescriptor(poolingDesc,
+                                                CUDNN_POOLING_MAX,
+                                                window_height,
+                                                window_width,
+                                                0,0, // no padding
+                                                stride_y,
+                                                stride_x));
+            }
+            catch(...)
+            {
+                clear();
+                throw;
+            }
         }
 
         void max_pool::
@@ -649,8 +671,8 @@ namespace dlib
 
             DLIB_CASSERT(dest.num_samples() == src.num_samples(),"");
             DLIB_CASSERT(dest.k() == src.k(),"");
-            DLIB_CASSERT(dest.nr() == src.nr()/stride_y,"");
-            DLIB_CASSERT(dest.nc() == src.nc()/stride_x,"");
+            DLIB_CASSERT(dest.nr() == src.nr()/stride_y, stride_y << ", " << dest.nr() << "  " << src.nr()/stride_y);
+            DLIB_CASSERT(dest.nc() == src.nc()/stride_x, stride_x << ", " << dest.nc() << "  " << src.nc()/stride_x);
 
             CHECK_CUDNN(cudnnPoolingForward(context(),
                                      (const cudnnPoolingDescriptor_t)handle,
@@ -673,7 +695,7 @@ namespace dlib
             DLIB_CASSERT(have_same_dimensions(src,grad),"");
 
             const float alpha = 1;
-            const float beta = 0;
+            const float beta = 1;
             CHECK_CUDNN(cudnnPoolingBackward(context(),
                                        (const cudnnPoolingDescriptor_t)handle,
                                        &alpha,
diff --git a/dlib/dnn/cudnn_dlibapi.h b/dlib/dnn/cudnn_dlibapi.h
index 55f6f41df..a95d0b300 100644
--- a/dlib/dnn/cudnn_dlibapi.h
+++ b/dlib/dnn/cudnn_dlibapi.h
@@ -328,6 +328,8 @@ namespace dlib
 
         private:
             void* handle;
+            int window_height;
+            int window_width;
             int stride_y;
             int stride_x;
         };