diff --git a/makepanda/makepanda.py b/makepanda/makepanda.py
index 09b86c201b..7adcfda7a3 100755
--- a/makepanda/makepanda.py
+++ b/makepanda/makepanda.py
@@ -956,7 +956,9 @@ def WriteConfigSettings():
         dtool_config["HAVE_PROC_SELF_MAPS"] = 'UNDEF'
         dtool_config["HAVE_PROC_SELF_CMDLINE"] = 'UNDEF'
         dtool_config["HAVE_PROC_SELF_ENVIRON"] = 'UNDEF'
-        # OSX still doesn't always recognize the <auto> correctly.
+        # OSX has ucontext.h, but it doesn't seem to be stable somehow.
+        dtool_config["HAVE_UCONTEXT_H"] = 'UNDEF'
+        # OSX still doesn't always recognize the <auto> correctly. Might have been fixed by now though.
         prc_parameters["DEFAULT_PRC_DIR"] = '"/Applications/Panda3D/' + VERSION + '/etc"'
     
     if (OPTIMIZE <= 3):