diff --git a/include/etl/private/to_string_helper.h b/include/etl/private/to_string_helper.h
index c1b630ba..60869664 100644
--- a/include/etl/private/to_string_helper.h
+++ b/include/etl/private/to_string_helper.h
@@ -218,7 +218,7 @@ namespace etl
     /// Helper function for floating point nan and inf.
     //***************************************************************************
     template <typename TIString>
-    void add_nan_inf(const bool not_a_number, const bool infinity, TIString& str, const etl::basic_format_spec<TIString>& format)
+    void add_nan_inf(const bool not_a_number, const bool infinity, const bool is_negative, TIString& str, const etl::basic_format_spec<TIString>& format)
     {
       typedef typename TIString::value_type type;
 
@@ -240,6 +240,11 @@ namespace etl
       }
       else if (infinity)
       {
+        if (is_negative)
+        {
+          str.push_back(type('-'));
+        }
+
         if (format.is_upper_case())
         {
           str.insert(str.end(), ETL_OR_STD11::begin(inf_upper), ETL_OR_STD11::end(inf_upper));
@@ -433,7 +438,7 @@ namespace etl
 
       if (isnan(value) || isinf(value))
       {
-        etl::private_to_string::add_nan_inf(isnan(value), isinf(value), str, format);
+        etl::private_to_string::add_nan_inf(isnan(value), isinf(value), etl::is_negative(value), str, format);
       }
       else
       {
diff --git a/test/test_to_string.cpp b/test/test_to_string.cpp
index 8dc05b72..17a9d982 100644
--- a/test/test_to_string.cpp
+++ b/test/test_to_string.cpp
@@ -28,7 +28,7 @@ SOFTWARE.
 
 #include "unit_test_framework.h"
 
-#include <format>
+#include <strstream>
 #include <iomanip>
 #include <ostream>
 
@@ -714,5 +714,36 @@ namespace
       CHECK(etl::string<64>(STR("                    0")) == s6);
 #endif
     }
+
+    //*************************************************************************
+    TEST(test_issue_1436_case_support_for_nan_inf_in_to_string)
+    {
+      if (std::numeric_limits<double>::is_iec559)
+      {
+        etl::string<64> s1;
+        etl::to_string(std::numeric_limits<double>::quiet_NaN(), s1, Format().precision(5).width(15).right().scientific(true).upper_case(false));
+        CHECK(etl::string<64>(STR("            nan")) == s1);
+
+        etl::string<64> s2;
+        etl::to_string(std::numeric_limits<double>::infinity(), s2, Format().precision(5).width(15).right().scientific(true).upper_case(false));
+        CHECK(etl::string<64>(STR("            inf")) == s2);
+
+        etl::string<64> s3;
+        etl::to_string(-std::numeric_limits<double>::infinity(), s3, Format().precision(5).width(15).right().scientific(true).upper_case(false));
+        CHECK(etl::string<64>(STR("           -inf")) == s3);
+
+        etl::string<64> s4;
+        etl::to_string(std::numeric_limits<double>::quiet_NaN(), s4, Format().precision(5).width(15).right().scientific(true).upper_case(true));
+        CHECK(etl::string<64>(STR("            NAN")) == s4);
+
+        etl::string<64> s5;
+        etl::to_string(std::numeric_limits<double>::infinity(), s5, Format().precision(5).width(15).right().scientific(true).upper_case(true));
+        CHECK(etl::string<64>(STR("            INF")) == s5);
+
+        etl::string<64> s6;
+        etl::to_string(-std::numeric_limits<double>::infinity(), s6, Format().precision(5).width(15).right().scientific(true).upper_case(true));
+        CHECK(etl::string<64>(STR("           -INF")) == s6);
+      }
+    }
   }
 } // namespace