diff --git a/opt.cpp b/opt.cpp
index c50f5f06..c66c69b1 100644
--- a/opt.cpp
+++ b/opt.cpp
@@ -79,7 +79,9 @@
   #include <alloca.h>
 #elif defined(ISPC_IS_WINDOWS)
   #include <malloc.h>
-  #define alloca _alloca
+  #ifndef __MINGW32__
+    #define alloca _alloca
+  #endif
 #endif // ISPC_IS_WINDOWS
 
 static llvm::Pass *CreateIntrinsicsOptPass();
diff --git a/util.cpp b/util.cpp
index f0d89c0d..34798a35 100644
--- a/util.cpp
+++ b/util.cpp
@@ -39,6 +39,9 @@
 #include "module.h"
 #ifdef ISPC_IS_WINDOWS
 #include <shlwapi.h>
+#ifdef __MINGW32__
+#include <malloc.h> // for alloca()
+#endif
 #else
 #include <alloca.h>
 #endif