diff --git a/cogl/cogl-sub-texture.c b/cogl/cogl-sub-texture.c
index bd23c857f..318282397 100644
--- a/cogl/cogl-sub-texture.c
+++ b/cogl/cogl-sub-texture.c
@@ -124,7 +124,7 @@ _cogl_sub_texture_unmap_coord (gfloat t,
   /* Convert the fractional part leaving the integer part in tact */
   frac_part = modff (t, &int_part);
 
-  if (signbit (frac_part))
+  if (cogl_util_float_signbit (frac_part))
     frac_part = ((1.0f + frac_part) * full_size -
                  sub_offset - sub_size) / sub_size;
   else
diff --git a/cogl/cogl-texture-2d.c b/cogl/cogl-texture-2d.c
index a86f84408..40f7b3f72 100644
--- a/cogl/cogl-texture-2d.c
+++ b/cogl/cogl-texture-2d.c
@@ -64,7 +64,7 @@ _cogl_texture_2d_wrap_coords (float t_1, float t_2,
   modff (t_1 < t_2 ? t_1 : t_2, &int_part);
   t_1 -= int_part;
   t_2 -= int_part;
-  if (signbit (int_part))
+  if (cogl_util_float_signbit (int_part))
     {
       *out_t_1 = 1.0f + t_1;
       *out_t_2 = 1.0f + t_2;
diff --git a/cogl/cogl-util.h b/cogl/cogl-util.h
index 589ddd35a..a6602a5f5 100644
--- a/cogl/cogl-util.h
+++ b/cogl/cogl-util.h
@@ -3,7 +3,7 @@
  *
  * An object oriented GL/GLES Abstraction/Utility Layer
  *
- * Copyright (C) 2007,2008,2009 Intel Corporation.
+ * Copyright (C) 2007,2008,2009,2010 Intel Corporation.
  *
  * This library is free software; you can redistribute it and/or
  * modify it under the terms of the GNU Lesser General Public
@@ -24,7 +24,32 @@
 #ifndef __COGL_UTIL_H
 #define __COGL_UTIL_H
 
+#include <glib.h>
+#include <math.h>
+
 int
 cogl_util_next_p2 (int a);
 
+/* The signbit macro is defined by ISO C99 so it should be available,
+   however if it's not we can fallback to an evil hack */
+#ifdef signbit
+#define cogl_util_float_signbit(x) signbit(x)
+#else
+/* This trick was stolen from here:
+   http://lists.boost.org/Archives/boost/2006/08/108731.php
+
+   It xors the integer reinterpretations of -1.0f and 1.0f. In theory
+   they should only differ by the signbit so that gives a mask for the
+   sign which we can just test against the value */
+static inline gboolean
+cogl_util_float_signbit (float x)
+{
+  static const union { float f; guint32 i; } negative_one = { -1.0f };
+  static const union { float f; guint32 i; } positive_one = { +1.0f };
+  union { float f; guint32 i; } value = { x };
+
+  return !!((negative_one.i ^ positive_one.i) & value.i);
+}
+#endif
+
 #endif /* __COGL_UTIL_H */