diff --git a/module.cpp b/module.cpp
index 8ad728b5..42c03fbe 100644
--- a/module.cpp
+++ b/module.cpp
@@ -184,7 +184,7 @@ Module::CompileFile() {
         FATAL("Need to implement code to run the preprocessor for windows"); 
 #else // ISPC_IS_WINDOWS
         char *cmd = NULL;
-        if (asprintf(&cmd, "/usr/bin/cpp -DISPC=1 -DPI=3.1415936535 %s %s", 
+        if (asprintf(&cmd, "/usr/bin/cpp -DISPC=1 -DPI=3.1415926536 %s %s", 
                      cppDefs.c_str(), filename ? filename : "-") == -1) {
             fprintf(stderr, "Unable to allocate memory in asprintf()?!\n");
             exit(1);
diff --git a/stdlib.ispc b/stdlib.ispc
index 629cdcd3..05abfd1a 100644
--- a/stdlib.ispc
+++ b/stdlib.ispc
@@ -1087,8 +1087,8 @@ static inline float atan2(float y, float x) {
     }
     else if (__math_lib == __math_lib_ispc || 
              __math_lib == __math_lib_ispc_fast) {
-        const float pi_vec = 3.1415927410125732421875;
-        const float pi_over_two_vec = 1.57079637050628662109375;
+        const float pi_vec = 3.1415926536;
+        const float pi_over_two_vec = 1.5707963267;
         // atan2(y, x) =
         //
         // atan2(y > 0, x = +-0) ->  Pi/2