diff --git a/extern/ttconv/pprdrv_tt.cpp b/extern/ttconv/pprdrv_tt.cpp
index a8428942ffe7..c0837a7d9d30 100644
--- a/extern/ttconv/pprdrv_tt.cpp
+++ b/extern/ttconv/pprdrv_tt.cpp
@@ -34,9 +34,11 @@
 #ifdef _POSIX_C_SOURCE
 #    undef _POSIX_C_SOURCE
 #endif
+#ifndef _AIX
 #ifdef _XOPEN_SOURCE
 #    undef _XOPEN_SOURCE
 #endif
+#endif
 #include <Python.h>
 
 /*==========================================================================
diff --git a/src/_png.cpp b/src/_png.cpp
index 574e1f645ef4..e7e2352c88dc 100644
--- a/src/_png.cpp
+++ b/src/_png.cpp
@@ -16,9 +16,11 @@ extern "C" {
 #   ifdef _POSIX_C_SOURCE
 #       undef _POSIX_C_SOURCE
 #   endif
+#   ifndef _AIX
 #   ifdef _XOPEN_SOURCE
 #       undef _XOPEN_SOURCE
 #   endif
+#   endif
 }
 
 #include "numpy_cpp.h"
diff --git a/src/mplutils.h b/src/mplutils.h
index 015daccea494..efb169023c61 100644
--- a/src/mplutils.h
+++ b/src/mplutils.h
@@ -14,9 +14,11 @@ typedef unsigned __int8   uint8_t;
 #ifdef _POSIX_C_SOURCE
 #    undef _POSIX_C_SOURCE
 #endif
+#ifndef _AIX
 #ifdef _XOPEN_SOURCE
 #    undef _XOPEN_SOURCE
 #endif
+#endif
 
 // Prevent multiple conflicting definitions of swab from stdlib.h and unistd.h
 #if defined(__sun) || defined(sun)
diff --git a/src/numpy_cpp.h b/src/numpy_cpp.h
index cddbcb6597d7..31774f97618d 100644
--- a/src/numpy_cpp.h
+++ b/src/numpy_cpp.h
@@ -21,9 +21,11 @@
 #ifdef _POSIX_C_SOURCE
 #    undef _POSIX_C_SOURCE
 #endif
+#ifndef _AIX
 #ifdef _XOPEN_SOURCE
 #    undef _XOPEN_SOURCE
 #endif
+#endif
 
 // Prevent multiple conflicting definitions of swab from stdlib.h and unistd.h
 #if defined(__sun) || defined(sun)