diff --git a/panda/src/glxdisplay/glxGraphicsPipe.cxx b/panda/src/glxdisplay/glxGraphicsPipe.cxx
index d67d809699..59f577a378 100644
--- a/panda/src/glxdisplay/glxGraphicsPipe.cxx
+++ b/panda/src/glxdisplay/glxGraphicsPipe.cxx
@@ -48,8 +48,15 @@ glxGraphicsPipe(const string &display) {
     display_spec = ":0.0";
   }
 
+  // The X docs say we should do this to get international character
+  // support from the keyboard.
   setlocale(LC_ALL, "");
 
+  // But it's important that we use the "C" locale for numeric
+  // formatting, since all of the internal Panda code assumes this--we
+  // need a decimal point to mean a decimal point.
+  setlocale(LC_NUMERIC, "C");
+
   _is_valid = false;
   _supported_types = OT_window | OT_buffer | OT_texture_buffer;
   _display = NULL;