diff --git a/src/main.cpp b/src/main.cpp
index 7143ef5..488d2ce 100644
--- a/src/main.cpp
+++ b/src/main.cpp
@@ -78,8 +78,10 @@ static void Run(const std::string& inputFile, const std::string& outputFile, con
 
         if (outputFile.ends_with(".svg"))
             Render<SvgRenderer>(shapes, outputFile, width, height);
-        else
+        else if (outputFile.ends_with(".pgm"))
             Render<PgmRenderer>(shapes, outputFile, width, height);
+        else
+            throw std::runtime_error("Unsupported output file format. Supported formats are .svg and .pgm");
 
         std::cout << "OK" << std::endl;
         std::cout << file.GetNumProcessedCmds() << std::endl;