diff --git a/srcpkgs/fox/patches/fix-cross-musl.patch b/srcpkgs/fox/patches/fix-cross-musl.patch
new file mode 100644
index 00000000000..27d938e45de
--- /dev/null
+++ b/srcpkgs/fox/patches/fix-cross-musl.patch
@@ -0,0 +1,13 @@
+Fix an obvious typo.
+
+--- src/FXString.cpp	2016-06-16 06:16:00.000000000 +0200
++++ src/FXString.cpp	2016-11-01 18:16:42.717595139 +0100
+@@ -2365,7 +2365,7 @@
+ #else
+     va_list ag;
+ x:  va_copy(ag,args);
+-    result=vsnprintf(str,length()+1,fmt,a);
++    result=vsnprintf(str,length()+1,fmt,ag);
+     va_end(ag);
+     if(result<0){ length(FXMAX(64,length()*2)); goto x; }
+     if(length()<result){ length(result); goto x; }