diff --git a/dnn/src/common/convolution.cpp b/dnn/src/common/convolution.cpp
index 0441f438..b5c66e90 100644
--- a/dnn/src/common/convolution.cpp
+++ b/dnn/src/common/convolution.cpp
@@ -777,8 +777,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
             src_or_dst_spatial_start = 1;
         }
         megdnn_assert(
-                cflt.icpg * cflt.group == src[src_or_dst_c_pos], "%s",
-                errmsg().c_str());
+                cflt.icpg * cflt.group == src[src_or_dst_c_pos],
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[src_or_dst_c_pos], cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         dst[src_or_dst_c_pos] = cflt.ocpg * cflt.group;
@@ -792,8 +794,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW4, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -809,8 +813,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW8, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 8, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 8,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 8, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -826,8 +832,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW32, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 32, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 32,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 32, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -856,7 +864,11 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
             megdnn_assert(
                     cflt.icpg * cflt.group == src[1] * 8 ||
                             (cflt.icpg * cflt.group == src[1]),
-                    "%s icpg=%u group=%u", errmsg().c_str(), cflt.icpg, cflt.group);
+                    "group conv channel mismatch : input channel got %zu, and "
+                    "filter channel got %u. More details about src, filter and dst : "
+                    "\n%s",
+                    src.ndim == 5 ? src[1] * 8 : src[1], cflt.icpg * cflt.group,
+                    errmsg().c_str());
         }
 
     } else if (
@@ -879,15 +891,21 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
             megdnn_assert(
                     cflt.icpg * cflt.group == src[1] * 4 ||
                             (cflt.icpg * cflt.group == src[1]),
-                    "%s icpg=%u group=%u", errmsg().c_str(), cflt.icpg, cflt.group);
+                    "group conv channel mismatch : input channel got %zu, and "
+                    "filter channel got %u. More details about src, filter and dst : "
+                    "\n%s",
+                    src.ndim == 5 ? src[1] * 4 : src[1], cflt.icpg * cflt.group,
+                    errmsg().c_str());
         }
     } else if (param().format == Param::Format::CHWN4) {
         megdnn_assert(
                 src.ndim == 5, "invalid src ndim for CHWN4, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[0] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[0] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[0] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[3] = src[3];
         auto oc = cflt.ocpg * cflt.group;
@@ -903,8 +921,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW4_NCHW, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = 4;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -918,8 +938,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW4_NHWC, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = 4;
         dst[0] = src[0];
         dst[1] = infer_conv_shape(
@@ -933,8 +955,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW4_NCHW32, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -950,8 +974,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW32_NCHW4, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 32, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 32,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 32, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -967,8 +993,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NCHW64, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[1] * 64, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[1] * 64,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[1] * 64, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
@@ -985,8 +1013,10 @@ typename ConvolutionBase<Parameter>::CanonizedFilterMeta ConvolutionBase<Paramet
                 src.ndim == 5, "invalid src ndim for NHWCD4, expected=5, got=%zu",
                 src.ndim);
         megdnn_assert(
-                cflt.icpg * cflt.group == src[2] * 4, "%s icpg=%u group=%u",
-                errmsg().c_str(), cflt.icpg, cflt.group);
+                cflt.icpg * cflt.group == src[2] * 4,
+                "group conv channel mismatch : input channel got %zu, and "
+                "filter channel got %u. More details for src, filter and dst : \n%s",
+                src[2] * 4, cflt.icpg * cflt.group, errmsg().c_str());
         dst.ndim = src.ndim;
         dst[0] = src[0];
         auto oc = cflt.ocpg * cflt.group;
diff --git a/dnn/src/common/convolution3d.cpp b/dnn/src/common/convolution3d.cpp
index 7ed86c33..035e36ff 100644
--- a/dnn/src/common/convolution3d.cpp
+++ b/dnn/src/common/convolution3d.cpp
@@ -148,7 +148,10 @@ Convolution3DBase::CanonizedFilterMeta Convolution3DBase::deduce_layout_fwd(
         src_or_dst_spatial_start = 1;
     }
     megdnn_assert(
-            cflt.icpg * cflt.group == src[src_or_dst_c_pos], "%s", errmsg().c_str());
+            cflt.icpg * cflt.group == src[src_or_dst_c_pos],
+            "group conv channel mismatch : input channel got %zu, and "
+            "filter channel got %u. More details about src, filter and dst : \n%s",
+            src[src_or_dst_c_pos], cflt.icpg * cflt.group, errmsg().c_str());
     dst.ndim = src.ndim;
     dst[0] = src[0];
     dst[src_or_dst_c_pos] = cflt.ocpg * cflt.group;