diff --git a/src/net.cpp b/src/net.cpp
index 2c3443dfb..6c77ac940 100644
--- a/src/net.cpp
+++ b/src/net.cpp
@@ -391,7 +391,11 @@ IMAGE_ALLOCATION_FAILED:
 
     if (image_allocation_failed)
     {
+#if NCNN_STRING
         NCNN_LOGE("forward_layer %d %s image allocation failed, fallback to cpu", layer_index, layer->name.c_str());
+#else
+        NCNN_LOGE("forward_layer %d image allocation failed, fallback to cpu", layer_index);
+#endif
     }
 
     if (layer->one_blob_only)
@@ -1607,6 +1611,8 @@ int Net::load_param_bin(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("ParamDict load_param %d %s failed", i, layer->name.c_str());
+#else
+            NCNN_LOGE("ParamDict load_param %d failed", i);
 #endif
             continue;
         }
@@ -1662,6 +1668,8 @@ int Net::load_param_bin(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("layer load_param %d %s failed", i, layer->name.c_str());
+#else
+            NCNN_LOGE("layer load_param %d failed", i);
 #endif
             continue;
         }
@@ -1696,6 +1704,8 @@ int Net::load_model(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("load_model error at layer %d %s, parameter file has inconsistent content.", i, layer->name.c_str());
+#else
+            NCNN_LOGE("load_model error at layer %d, parameter file has inconsistent content.", i);
 #endif
             ret = -1;
             break;
@@ -1706,6 +1716,8 @@ int Net::load_model(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("layer load_model %d %s failed", i, layer->name.c_str());
+#else
+            NCNN_LOGE("layer load_model %d failed", i);
 #endif
             ret = -1;
             break;
@@ -1739,6 +1751,8 @@ int Net::load_model(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("load_model error at layer %d %s, parameter file has inconsistent content.", i, layer->name.c_str());
+#else
+            NCNN_LOGE("load_model error at layer %d, parameter file has inconsistent content.", i);
 #endif
             ret = -1;
             break;
@@ -1757,6 +1771,8 @@ int Net::load_model(const DataReader& dr)
         {
 #if NCNN_STRING
             NCNN_LOGE("layer create_pipeline %d %s failed", i, layer->name.c_str());
+#else
+            NCNN_LOGE("layer create_pipeline %d failed", i);
 #endif
             ret = -1;
             break;
diff --git a/tools/modelwriter.h b/tools/modelwriter.h
index c40f8cf25..8614a97e3 100644
--- a/tools/modelwriter.h
+++ b/tools/modelwriter.h
@@ -1592,7 +1592,7 @@ int ModelWriter::save(const char* parampath, const char* binpath)
 
     if (mac)
     {
-        fprintf(stderr, "mac = %lld = %.2f M\n", mac, mac / 1000000.0);
+        fprintf(stderr, "mac = %llu = %.2f M\n", mac, mac / 1000000.0);
     }
 
     return 0;