diff --git a/.github/workflows/msys2-cross-compile.yml b/.github/workflows/msys2-cross-compile.yml
index 9da5cf8..770ea3b 100644
--- a/.github/workflows/msys2-cross-compile.yml
+++ b/.github/workflows/msys2-cross-compile.yml
@@ -2,7 +2,7 @@ name: MSYS2
 on: [push, pull_request]
 
 jobs:
-  msys2-ucrt64:
+  msys2-mingw64:
     runs-on: windows-latest
     defaults:
       run:
diff --git a/src/ast/ast.c b/src/ast/ast.c
index 4e3ba6f..6de0c74 100644
--- a/src/ast/ast.c
+++ b/src/ast/ast.c
@@ -219,6 +219,7 @@ void AST_delete_node(struct AST_Node_t *node) {
   }
 
   if (node->parent != NULL) {
+    [[maybe_unused]]
     const struct AST_Node_t* child = AST_detach_child(node->parent, node);
     assert(child == node);
   }
diff --git a/src/io/files.c b/src/io/files.c
index 5f3ad02..d2c889b 100644
--- a/src/io/files.c
+++ b/src/io/files.c
@@ -16,6 +16,8 @@
 #elif defined(_WIN32) || defined(WIN32)
 
 #include <Windows.h>
+// for _fullpath
+#include <stdlib.h>
 
 #define MAX_PATH_BYTES _MAX_PATH
 
@@ -122,15 +124,15 @@ void print_diagnostic(ModuleFile *file, TokenLocation *location, Message kind, c
 
     free((void *) absolute_path);
 
-    const size_t lines = location->line_end - location->line_start + 1;
+    const unsigned long int lines = location->line_end - location->line_start + 1;
 
-    for (size_t l = 0; l < lines; l++) {
+    for (unsigned long int l = 0; l < lines; l++) {
         printf(" %4ld | ", location->line_start + l);
 
-        size_t chars = 0;
+        unsigned long int chars = 0;
 
         // print line before token group start
-        size_t limit = min(location->col_start, SEEK_BUF_BYTES);
+        unsigned long int limit = min(location->col_start, SEEK_BUF_BYTES);
         while (limit > 1) {
             custom_fgets(buffer, (int) limit, file->handle);
             chars += printf("%s", buffer);
@@ -168,13 +170,13 @@ void print_diagnostic(ModuleFile *file, TokenLocation *location, Message kind, c
     }
 
     printf("      | ");
-    for (size_t i = 1; i < location->col_start; i++) {
+    for (unsigned long int i = 1; i < location->col_start; i++) {
         printf(" ");
     }
 
     printf("%s", accent_color);
     printf("^");
-    for (size_t i = 0; i < location->col_end - location->col_start; i++) {
+    for (unsigned long int i = 0; i < location->col_end - location->col_start; i++) {
         printf("~");
     }
 
@@ -320,7 +322,7 @@ const char *get_absolute_path(const char *path) {
 #elif defined(_WIN32) || defined(WIN32)
     // use Windows CRT specific function
     char absolute_path[MAX_PATH_BYTES];
-    _fullpath(path, absolute_path, _MAX_PATH);
+    _fullpath((char*) path, absolute_path, _MAX_PATH);
 #endif
 
     return strdup(absolute_path);
diff --git a/src/io/files.h b/src/io/files.h
index 61c7ebb..c05f587 100644
--- a/src/io/files.h
+++ b/src/io/files.h
@@ -15,9 +15,9 @@
 #endif
 
 typedef struct FileDiagnosticStatistics_t {
-    size_t error_count;
-    size_t warning_count;
-    size_t info_count;
+    unsigned long int error_count;
+    unsigned long int warning_count;
+    unsigned long int info_count;
 } FileDiagnosticStatistics;
 
 typedef struct ModuleFile_t {