diff --git a/src/ccutil/unicharset.cpp b/src/ccutil/unicharset.cpp
index c0aea1f3e6..b29ec3b7fe 100644
--- a/src/ccutil/unicharset.cpp
+++ b/src/ccutil/unicharset.cpp
@@ -824,7 +824,7 @@ bool UNICHARSET::load_via_fgets(
     stream >> std::setw(255) >> unichar >> std::hex >> properties >> std::dec;
     // stream.flags(std::ios::dec);
     if (stream.fail()) {
-      fprintf(stderr, "%s:%u failed\n", __FILE__, __LINE__);
+      fprintf(stderr, "%s:%d failed\n", __FILE__, __LINE__);
       return false;
     }
     auto position = stream.tellg();
diff --git a/src/classify/clusttool.cpp b/src/classify/clusttool.cpp
index 543378d6b3..de8b1f5cb8 100644
--- a/src/classify/clusttool.cpp
+++ b/src/classify/clusttool.cpp
@@ -277,7 +277,7 @@ void WritePrototype(FILE *File, uint16_t N, PROTOTYPE *Proto) {
     fprintf(File, "insignificant ");
   }
   WriteProtoStyle(File, static_cast<PROTOSTYLE>(Proto->Style));
-  fprintf(File, "%6d\n\t", Proto->NumSamples);
+  fprintf(File, "%6u\n\t", Proto->NumSamples);
   WriteNFloats(File, N, &Proto->Mean[0]);
   fprintf(File, "\t");
 
diff --git a/src/viewer/scrollview.cpp b/src/viewer/scrollview.cpp
index f5336c589a..73bd3c5fc2 100644
--- a/src/viewer/scrollview.cpp
+++ b/src/viewer/scrollview.cpp
@@ -307,7 +307,7 @@ void ScrollView::Initialize(const char *name, int x_pos, int y_pos, int x_size,
   // Set up an actual Window on the client side.
   char message[kMaxMsgSize];
   snprintf(message, sizeof(message),
-           "w%u = luajava.newInstance('com.google.scrollview.ui"
+           "w%d = luajava.newInstance('com.google.scrollview.ui"
            ".SVWindow','%s',%u,%u,%u,%u,%u,%u,%u)\n",
            window_id_, window_name_, window_id_, x_pos, y_pos, x_size, y_size, x_canvas_size,
            y_canvas_size);
@@ -393,7 +393,7 @@ void ScrollView::SendMsg(const char *format, ...) {
   va_end(args);
 
   char form[kMaxMsgSize];
-  snprintf(form, sizeof(form), "w%u:%s\n", window_id_, message);
+  snprintf(form, sizeof(form), "w%d:%s\n", window_id_, message);
 
   stream_->Send(form);
 }
@@ -532,7 +532,7 @@ void ScrollView::AlwaysOnTop(bool b) {
 // Adds a message entry to the message box.
 void ScrollView::AddMessage(const char *message) {
   char form[kMaxMsgSize];
-  snprintf(form, sizeof(form), "w%u:%s", window_id_, message);
+  snprintf(form, sizeof(form), "w%d:%s", window_id_, message);
 
   char *esc = AddEscapeChars(form);
   SendMsg("addMessage(\"%s\")", esc);