diff --git a/arm9/lib/MSL_C/include/MSL.h b/arm9/lib/MSL_C/include/MSL.h
index a21bbc756..f3287f28e 100644
--- a/arm9/lib/MSL_C/include/MSL.h
+++ b/arm9/lib/MSL_C/include/MSL.h
@@ -3,8 +3,8 @@
 
 //include all msl files here
 
-#include "string.h"
-#include "arith.h"
 #include "rand.h"
+#include "stdlib.h"
+#include "string.h"
 
 #endif //MSL_H
diff --git a/arm9/lib/MSL_C/include/arith.h b/arm9/lib/MSL_C/include/arith.h
deleted file mode 100644
index b998fb728..000000000
--- a/arm9/lib/MSL_C/include/arith.h
+++ /dev/null
@@ -1,6 +0,0 @@
-#ifndef POKEDIAMOND_MSL_C_ARITH_H
-#define POKEDIAMOND_MSL_C_ARITH_H
-
-int abs(int val);
-
-#endif //POKEDIAMOND_MSL_C_ARITH_H
diff --git a/arm9/lib/MSL_C/include/stdlib.h b/arm9/lib/MSL_C/include/stdlib.h
new file mode 100644
index 000000000..21772e8b7
--- /dev/null
+++ b/arm9/lib/MSL_C/include/stdlib.h
@@ -0,0 +1,8 @@
+#ifndef POKEDIAMOND_MSL_C_STDLIB_H
+#define POKEDIAMOND_MSL_C_STDLIB_H
+
+// this file MUST be called stdlib.h, as the filename affects matching for some reason
+
+int abs(int val);
+
+#endif // POKEDIAMOND_MSL_C_STDLIB_H
diff --git a/arm9/lib/MSL_C/src/arith.c b/arm9/lib/MSL_C/src/arith.c
index 33d315005..57373cca1 100644
--- a/arm9/lib/MSL_C/src/arith.c
+++ b/arm9/lib/MSL_C/src/arith.c
@@ -1,5 +1,5 @@
-#include "arith.h"
 #include "code32.h"
+#include "stdlib.h"
 
 int abs(int val) {
     return val < 0 ? -val : val;