diff --git a/lib/libc/gen/isnan.c b/lib/libc/gen/isnan.c
index e17d915e0ad3..ea84c7ebe403 100644
--- a/lib/libc/gen/isnan.c
+++ b/lib/libc/gen/isnan.c
@@ -43,6 +43,13 @@
  */
 
 #ifdef PIC
+/*
+ * Because math.h defines __isnan and __isnanf as aliases for compatibility with
+ * glibc and CUDA, we have to undefine them here to avoid redefinition errors.
+ */
+#undef __isnan
+#undef __isnanf
+
 __weak_reference(__isnan, isnan);
 __weak_reference(__isnanf, isnanf);
 
diff --git a/lib/msun/src/math.h b/lib/msun/src/math.h
index a8f45544c475..6ce45cbb5280 100644
--- a/lib/msun/src/math.h
+++ b/lib/msun/src/math.h
@@ -214,6 +214,12 @@ __inline_isnanl(__const long double __x)
 	return (__x != __x);
 }
 
+/*
+ * Define the following aliases, for compatibility with glibc and CUDA.
+ */
+#define __isnan __inline_isnan
+#define __isnanf __inline_isnanf
+
 /*
  * Version 2 of the Single UNIX Specification (UNIX98) defined isnan() and
  * isinf() as functions taking double.  C99, and the subsequent POSIX revisions
diff --git a/lib/msun/src/s_isnan.c b/lib/msun/src/s_isnan.c
index 249c00615748..ea3c8db67da6 100644
--- a/lib/msun/src/s_isnan.c
+++ b/lib/msun/src/s_isnan.c
@@ -45,6 +45,12 @@ isnan(double d)
 }
 #endif /* !PIC */
 
+/*
+ * Because math.h defines __isnanf as an alias for compatibility with glibc and
+ * CUDA, we have to undefine it here to avoid redefinition errors.
+ */
+#undef __isnanf
+
 int
 __isnanf(float f)
 {