diff --git a/cmake/SundialsSetupCompilers.cmake b/cmake/SundialsSetupCompilers.cmake
index f0e109932d..1d2873b6e7 100644
--- a/cmake/SundialsSetupCompilers.cmake
+++ b/cmake/SundialsSetupCompilers.cmake
@@ -120,20 +120,6 @@ set(DOCSTR "Enable C compiler specific extensions")
 sundials_option(CMAKE_C_EXTENSIONS BOOL "${DOCSTR}" ON)
 message(STATUS "C extensions set to ${CMAKE_C_EXTENSIONS}")
 
-# ---------------------------------------------------------------
-# Check for isinf and isnan
-# ---------------------------------------------------------------
-
-check_c_source_compiles("
-  #include <math.h>
-  int main(void) {
-    double a = 0.0;
-    int result = isinf(a);
-    result = isnan(a);
-    return result;
-  }
-" SUNDIALS_C_COMPILER_HAS_ISINF_ISNAN)
-
 # ---------------------------------------------------------------
 # Check for __builtin_expect
 # ---------------------------------------------------------------
diff --git a/examples/sunlinsol/test_sunlinsol.c b/examples/sunlinsol/test_sunlinsol.c
index 46463afc4d..2a6900e666 100644
--- a/examples/sunlinsol/test_sunlinsol.c
+++ b/examples/sunlinsol/test_sunlinsol.c
@@ -20,7 +20,7 @@
 
 #include "test_sunlinsol.h"
 
-#include <math.h> /* include isnan */
+#include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sundials/sundials_linearsolver.h>
diff --git a/examples/sunmatrix/test_sunmatrix.c b/examples/sunmatrix/test_sunmatrix.c
index d9c9fb754a..f6041c1983 100644
--- a/examples/sunmatrix/test_sunmatrix.c
+++ b/examples/sunmatrix/test_sunmatrix.c
@@ -20,7 +20,7 @@
 
 #include "test_sunmatrix.h"
 
-#include <math.h> /* include isnan */
+#include <math.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <sundials/sundials_math.h>
diff --git a/include/sundials/sundials_config.in b/include/sundials/sundials_config.in
index db3a6268d6..25d2fe8e78 100644
--- a/include/sundials/sundials_config.in
+++ b/include/sundials/sundials_config.in
@@ -56,7 +56,6 @@
  * SUNDIALS build information
  * -----------------------------------------------------------------*/
 
-#cmakedefine SUNDIALS_C_COMPILER_HAS_ISINF_ISNAN
 #cmakedefine SUNDIALS_C_COMPILER_HAS_BUILTIN_EXPECT
 #cmakedefine SUNDIALS_C_COMPILER_HAS_ATTRIBUTE_ASSUME
 #cmakedefine SUNDIALS_C_COMPILER_HAS_BUILTIN_ASSUME
diff --git a/src/sundials/sundials_math.c b/src/sundials/sundials_math.c
index dfd4aaf6a4..b60e9c2540 100644
--- a/src/sundials/sundials_math.c
+++ b/src/sundials/sundials_math.c
@@ -22,28 +22,6 @@
 #include <sundials/sundials_math.h>
 #include <sundials/sundials_types.h>
 
-static sunbooleantype sunIsInf(sunrealtype a)
-{
-#if defined(__cplusplus) || defined(SUNDIALS_C_COMPILER_HAS_ISINF_ISNAN)
-  return (isinf(a));
-#else
-  return (a < -SUN_BIG_REAL || a > SUN_BIG_REAL);
-#endif
-}
-
-static sunbooleantype sunIsNaN(sunrealtype a)
-{
-#if defined(__cplusplus) || defined(SUNDIALS_C_COMPILER_HAS_ISINF_ISNAN)
-  return (isnan(a));
-#else
-  /* Most compilers/platforms follow NaN != a,
-   * but since C89 does not require this, it is
-   * possible some platforms might not follow it.
-   */
-  return (a != a);
-#endif
-}
-
 sunrealtype SUNRpowerI(sunrealtype base, int exponent)
 {
   int i, expt;
@@ -88,10 +66,10 @@ sunbooleantype SUNRCompareTol(sunrealtype a, sunrealtype b, sunrealtype tol)
   if (a == b) { return (SUNFALSE); }
 
   /* If a or b are NaN */
-  if (sunIsNaN(a) || sunIsNaN(b)) { return (SUNTRUE); }
+  if (isnan(a) || isnan(b)) { return (SUNTRUE); }
 
   /* If one of a or b are Inf (since we handled both being inf above) */
-  if (sunIsInf(a) || sunIsInf(b)) { return (SUNTRUE); }
+  if (isinf(a) || isinf(b)) { return (SUNTRUE); }
 
   diff = SUNRabs(a - b);
   norm = SUNMIN(SUNRabs(a + b), SUN_BIG_REAL);