diff --git a/include/mpg123/OpenMPT.txt b/include/mpg123/OpenMPT.txt
index 7b6d72397fd..d8b9a6b40aa 100644
--- a/include/mpg123/OpenMPT.txt
+++ b/include/mpg123/OpenMPT.txt
@@ -6,6 +6,7 @@ The following changes have been made:
  *  `ports/Xcode/config.h` has been modified to let the build system set
     `OPT_*`.
  *  `ports/Xcode/config.h` has been modified to `#define HAVE_DIRENT_H`.
+ *  `src/compat/compat.c` has been modified for DJGPP compatibility.
  *  Modifications are marked by `// OpenMPT` or `/* OpenMPT */`.
  *  Obviously, unnecessary folders and files have been removed.
  *  For building, premake is used to generate Visual Studio project files.
diff --git a/include/mpg123/src/compat/compat.c b/include/mpg123/src/compat/compat.c
index 09983ca4dfd..2cc3760c04b 100644
--- a/include/mpg123/src/compat/compat.c
+++ b/include/mpg123/src/compat/compat.c
@@ -10,8 +10,10 @@
 */
 
 #include "config.h"
+#if !defined(__DJGPP__)  /* OpenMPT */
 /* This source file does need _POSIX_SOURCE to get some sigaction. */
 #define _POSIX_SOURCE
+#endif  /* OpenMPT */
 #include "compat.h"
 
 #ifdef _MSC_VER