diff --git a/include/fast_float/float_common.h b/include/fast_float/float_common.h
index 73e44c4..bb79dc8 100644
--- a/include/fast_float/float_common.h
+++ b/include/fast_float/float_common.h
@@ -124,7 +124,7 @@ struct span {
   span(const T* _ptr, size_t _length) : ptr(_ptr), length(_length) {}
   span() : ptr(nullptr), length(0) {}
 
-  constexpr size_t len() noexcept {
+  constexpr size_t len() const noexcept {
     return length;
   }
 
diff --git a/tests/long_exhaustive32_64.cpp b/tests/long_exhaustive32_64.cpp
index 5f7dafd..0a58895 100644
--- a/tests/long_exhaustive32_64.cpp
+++ b/tests/long_exhaustive32_64.cpp
@@ -30,7 +30,12 @@ void all_32bit_values() {
         std::cerr << "parsing error ? " << buffer << std::endl;
         abort();
       }
-      if(copysign(1,result_value) != copysign(1,v)) {
+      if (std::isnan(v)) {
+        if (!std::isnan(result_value)) {
+          std::cerr << "not nan" << buffer << std::endl;
+          abort();
+        }
+      } else if(copysign(1,result_value) != copysign(1,v)) {
         std::cerr << "I got " << std::hexfloat << result_value << " but I was expecting " << v
               << std::endl;
         abort();
diff --git a/tests/string_test.cpp b/tests/string_test.cpp
index 20f159a..53f17a4 100644
--- a/tests/string_test.cpp
+++ b/tests/string_test.cpp
@@ -59,6 +59,7 @@ bool test() {
   const char * end = input.data() + input.size();
   for(size_t i = 0; i < answers.size(); i++) {
     T result_value;
+    while((begin < end) && (std::isspace(*begin))) { begin++; }
     auto result = fast_float::from_chars(begin, end,
                                       result_value);
     if (result.ec != std::errc()) {