diff --git a/mozilla/gfx/cairo/cairo/src/cairo-gstate.c b/mozilla/gfx/cairo/cairo/src/cairo-gstate.c
index a00a52c12da..4256d3829da 100644
--- a/mozilla/gfx/cairo/cairo/src/cairo-gstate.c
+++ b/mozilla/gfx/cairo/cairo/src/cairo-gstate.c
@@ -42,7 +42,7 @@
 #include "cairo-clip-private.h"
 #include "cairo-gstate-private.h"
 
-#if _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
+#if _XOPEN_SOURCE >= 600 || defined(_ISOC99_SOURCE) 
 #define ISFINITE(x) isfinite (x)
 #else
 #define ISFINITE(x) ((x) * (x) >= 0.) /* check for NaNs */
diff --git a/mozilla/gfx/cairo/cairo/src/cairo-matrix.c b/mozilla/gfx/cairo/cairo/src/cairo-matrix.c
index c3578a298b2..953dcba82c8 100644
--- a/mozilla/gfx/cairo/cairo/src/cairo-matrix.c
+++ b/mozilla/gfx/cairo/cairo/src/cairo-matrix.c
@@ -38,7 +38,7 @@
 
 #include "cairoint.h"
 
-#if _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE
+#if _XOPEN_SOURCE >= 600 || defined(_ISOC99_SOURCE)
 #define ISFINITE(x) isfinite (x)
 #else
 #define ISFINITE(x) ((x) * (x) >= 0.) /* check for NaNs */