diff --git a/src/arc/lexer.cpp b/src/arc/lexer.cpp
index c63e2466..d571699d 100644
--- a/src/arc/lexer.cpp
+++ b/src/arc/lexer.cpp
@@ -84,6 +84,8 @@ auto lexer::lex() -> token
                     }
                     else
                     {
+                        auto first = true;
+
                         while (true)
                         {
                             if (reader_.ended())
@@ -94,18 +96,21 @@ auto lexer::lex() -> token
                                 loc_.lines();
                                 loc_.step();
                             }
-                            else if (last == '#' && curr == '/')
+                            else if (last == '#' && curr == '/' && !first)
                             {
                                 advance();
                                 break;
                             }
 
                             advance();
+                            first = false;
                         }
                     }
                 }
                 else if (last == '@')
                 {
+                    auto first = true;
+
                     while (true)
                     {
                         if (reader_.ended())
@@ -116,17 +121,20 @@ auto lexer::lex() -> token
                             loc_.lines();
                             loc_.step();
                         }
-                        else if (last == '@' && curr == '/')
+                        else if (last == '@' && curr == '/' && !first)
                         {
                             advance();
                             break;
                         }
 
                         advance();
+                        first = false;
                     }
                 }
                 else if (last == '*')
                 {
+                    auto first = true;
+
                     while (true)
                     {
                         if (reader_.ended())
@@ -137,13 +145,14 @@ auto lexer::lex() -> token
                             loc_.lines();
                             loc_.step();
                         }
-                        else if (last  == '*' && curr == '/')
+                        else if (last  == '*' && curr == '/' && !first)
                         {
                             advance();
                             break;
                         }
 
                         advance();
+                        first = false;
                     }
                 }
                 else if (last == '/')
diff --git a/src/gsc/lexer.cpp b/src/gsc/lexer.cpp
index 344b4218..759fbf32 100644
--- a/src/gsc/lexer.cpp
+++ b/src/gsc/lexer.cpp
@@ -84,6 +84,8 @@ auto lexer::lex() -> token
                     }
                     else
                     {
+                        auto first = true;
+
                         while (true)
                         {
                             if (reader_.ended())
@@ -94,18 +96,21 @@ auto lexer::lex() -> token
                                 loc_.lines();
                                 loc_.step();
                             }
-                            else if (last == '#' && curr == '/')
+                            else if (last == '#' && curr == '/' && !first)
                             {
                                 advance();
                                 break;
                             }
 
                             advance();
+                            first = false;
                         }
                     }
                 }
                 else if (last == '@')
                 {
+                    auto first = true;
+
                     while (true)
                     {
                         if (reader_.ended())
@@ -116,17 +121,20 @@ auto lexer::lex() -> token
                             loc_.lines();
                             loc_.step();
                         }
-                        else if (last == '@' && curr == '/')
+                        else if (last == '@' && curr == '/' && !first)
                         {
                             advance();
                             break;
                         }
 
                         advance();
+                        first = false;
                     }
                 }
                 else if (last == '*')
                 {
+                    auto first = true;
+
                     while (true)
                     {
                         if (reader_.ended())
@@ -137,13 +145,14 @@ auto lexer::lex() -> token
                             loc_.lines();
                             loc_.step();
                         }
-                        else if (last  == '*' && curr == '/')
+                        else if (last  == '*' && curr == '/' && !first)
                         {
                             advance();
                             break;
                         }
 
                         advance();
+                        first = false;
                     }
                 }
                 else if (last == '/')
diff --git a/src/tool/main.cpp b/src/tool/main.cpp
index 3653b723..8f4170b0 100644
--- a/src/tool/main.cpp
+++ b/src/tool/main.cpp
@@ -781,6 +781,13 @@ auto assemble_file(game game, mach mach, fs::path const& file, fs::path rel) ->
         rel = fs::path{ games_rev.at(game) } / rel / file.filename().replace_extension((file.extension() == ".gscasm" ? ".gsc" : ".csc"));
 
         auto data = utils::file::read(file);
+
+        if (data.size() >= 4 && !std::memcmp(&data[0], "\x80GSC", 4))
+        {
+            std::cerr << std::format("{} at {}\n", "already assembled", file.generic_string());
+            return result::success;
+        }
+
         auto outasm = contexts[game][mach]->source().parse_assembly(data);
         auto outbin = contexts[game][mach]->assembler().assemble(*outasm);
 
@@ -834,7 +841,7 @@ auto compile_file(game game, mach mach, fs::path const& file, fs::path rel) -> r
 
         auto data = utils::file::read(file);
 
-        if (!std::memcmp(&data[0], "\x80GSC", 4))
+        if (data.size() >= 4 && !std::memcmp(&data[0], "\x80GSC", 4))
         {
             std::cerr << std::format("{} at {}\n", "already compiled", file.generic_string());
             return result::success;
@@ -904,7 +911,7 @@ auto parse_file(game game, mach mach, fs::path file, fs::path rel) -> result
 
         auto data = utils::file::read(file);
 
-        if (!std::memcmp(&data[0], "\x80GSC", 4))
+        if (data.size() >= 4 && !std::memcmp(&data[0], "\x80GSC", 4))
         {
             std::cerr << std::format("{} at {}\n", "already compiled", file.generic_string());
             return result::success;