diff --git a/include/polyscope/render/mock_opengl/mock_gl_engine.h b/include/polyscope/render/mock_opengl/mock_gl_engine.h
index df2651c7..6560902c 100644
--- a/include/polyscope/render/mock_opengl/mock_gl_engine.h
+++ b/include/polyscope/render/mock_opengl/mock_gl_engine.h
@@ -328,6 +328,9 @@ class MockGLEngine : public Engine {
   virtual void shutdown() override;
   void checkError(bool fatal = false) override;
 
+  // mock backend is always headless
+  virtual bool isHeadless() override { return true; }
+
   void swapDisplayBuffers() override;
   std::vector<unsigned char> readDisplayBuffer() override;
 
diff --git a/src/messages.cpp b/src/messages.cpp
index 093689b4..a936d7ae 100644
--- a/src/messages.cpp
+++ b/src/messages.cpp
@@ -233,8 +233,11 @@ void terminatingError(std::string message) {
     std::cout << options::printPrefix << "[ERROR] " << message << std::endl;
   }
 
-  auto func = std::bind(buildErrorUI, message, true);
-  pushContext(func, false);
+  // Enter a modal UI loop showing the warning
+  if (!isHeadless()) { // don't do it if running headless
+    auto func = std::bind(buildErrorUI, message, true);
+    pushContext(func, false);
+  }
 
   // Quit the program
   shutdown(true);
@@ -243,6 +246,13 @@ void terminatingError(std::string message) {
 
 void warning(std::string baseMessage, std::string detailMessage) {
 
+  // print to stdout
+  if (options::verbosity > 0) {
+    std::cout << options::printPrefix << "[WARNING] " << baseMessage;
+    if (detailMessage != "") std::cout << " --- " << detailMessage;
+    std::cout << std ::endl;
+  }
+
   // Look for a message with the same name
   bool found = false;
   for (WarningMessage& w : warningMessages) {
@@ -268,16 +278,13 @@ void showDelayedWarnings() {
     showingWarning = true;
     WarningMessage& currMessage = warningMessages.front();
 
-    if (options::verbosity > 0) {
-      std::cout << options::printPrefix << "[WARNING] " << currMessage.baseMessage;
-      if (currMessage.detailMessage != "") std::cout << " --- " << currMessage.detailMessage;
-      if (currMessage.repeatCount > 0) std::cout << " (and " << currMessage.repeatCount << " similar messages).";
-      std::cout << std ::endl;
+    // Enter a modal UI loop showing the warning
+    if (!isHeadless()) { // don't do it if running headless
+      auto func =
+          std::bind(buildWarningUI, currMessage.baseMessage, currMessage.detailMessage, currMessage.repeatCount);
+      pushContext(func, false);
     }
 
-    auto func = std::bind(buildWarningUI, currMessage.baseMessage, currMessage.detailMessage, currMessage.repeatCount);
-    pushContext(func, false);
-
     warningMessages.pop_front();
     showingWarning = false;
   }