diff --git a/liba/include/math.h b/liba/include/math.h
index a06b45113..74c48538e 100644
--- a/liba/include/math.h
+++ b/liba/include/math.h
@@ -5,8 +5,16 @@
 
 LIBA_BEGIN_DECLS
 
+/* The C99 standard requires isinf and isnan to be defined as macros that can
+ * handle arbitrary precision float numbers. The names of the functions called
+ * by those macros (depending on the argument size) are not standardized though.
+ * We're chosing isinff/isnanf for single-precision functions (which is the only
+ * case we're actually handling). */
+
 int isinff(float x);
+#define isinf(x) isinff(x)
 int isnanf(float x);
+#define isnan(x) isnanf(x)
 
 float copysignf(float x, float y);
 float cosf(float x);