diff --git a/CMakeLists.txt b/CMakeLists.txt
index 10a011314..fe8004a5f 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -123,6 +123,9 @@ file(GLOB
 list(FILTER LIBS_INCLUDE EXCLUDE REGEX "zlib|libzip|libressl")
 target_include_directories(${PROJECT_NAME} PRIVATE ${LIBS_INCLUDE})
 
+# allow FASTFLOAT_ALLOWS_LEADING_PLUS
+add_definitions(-DFASTFLOAT_ALLOWS_LEADING_PLUS=1)
+
 target_include_directories(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR_AUTOGENERATED}/Source)
 target_include_directories(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/Include/API)
 target_include_directories(${PROJECT_NAME} PRIVATE ${CMAKE_CURRENT_SOURCE_DIR}/Include)
diff --git a/Source/Common/NMR_StringUtils.cpp b/Source/Common/NMR_StringUtils.cpp
index 63166d6e8..7c663e492 100644
--- a/Source/Common/NMR_StringUtils.cpp
+++ b/Source/Common/NMR_StringUtils.cpp
@@ -161,7 +161,13 @@ namespace NMR {
 		{
 			throw CNMRException(NMR_ERROR_EMPTYSTRINGTODOUBLECONVERSION);
 		}
-		
+		else if (answer.ptr) // Invalidate comma as decimal separator
+		{
+			if (answer.ptr[0] == ',')
+			{
+				throw CNMRException(NMR_ERROR_INVALIDSTRINGTODOUBLECONVERSION);
+			}
+		}
 		if ((dResult == HUGE_VAL) || (dResult == -HUGE_VAL))
 			throw CNMRException(NMR_ERROR_STRINGTODOUBLECONVERSIONOUTOFRANGE);
 
diff --git a/Tests/CPP_Bindings/Source/Reader.cpp b/Tests/CPP_Bindings/Source/Reader.cpp
index fa2c81b89..03e4b4698 100644
--- a/Tests/CPP_Bindings/Source/Reader.cpp
+++ b/Tests/CPP_Bindings/Source/Reader.cpp
@@ -149,4 +149,21 @@ namespace Lib3MF
 		auto reader = model->QueryReader("3mf");
 		ASSERT_SPECIFIC_THROW(reader->ReadFromFile(sTestFilesPath + "/Reader/" + "GEN-M-ADA-ITEM-TRANSFORM-0.3mf"), ELib3MFException);
 	}
+
+
+	TEST_F(Reader, ReadVerticesCommaSeparatedValue) {
+		// This file N_XXX_0422_01.3mf contains vertices with comma-separated values.
+		// The 3MFReader should throw an error at NMR_StringUtils::fnStringToDouble when reading this file because 
+		// comma-separated values are not allowed in 3MF files.
+		auto reader = model->QueryReader("3mf");
+		ASSERT_SPECIFIC_THROW(reader->ReadFromFile(sTestFilesPath + "/Reader/" + "N_XXX_0422_01.3mf"), ELib3MFException);
+	}
+
+	TEST_F(Reader, ReadVerticesWithLeadingPLUSSign) {
+		// This file P_XXM_0519_01.3mf contains vertices with leading + sign e.g +1E+2.
+		// The 3MFReader allows leading = sign at NMR_StringUtils::fnStringToDouble when reading this file.
+		auto reader = model->QueryReader("3mf");
+		reader->ReadFromFile(sTestFilesPath + "/Reader/" + "P_XXM_0519_01.3mf");
+		CheckReaderWarnings(Reader::reader3MF, 0);
+	}
 }
diff --git a/Tests/TestFiles/Reader/N_XXX_0422_01.3mf b/Tests/TestFiles/Reader/N_XXX_0422_01.3mf
new file mode 100644
index 000000000..b10793a27
Binary files /dev/null and b/Tests/TestFiles/Reader/N_XXX_0422_01.3mf differ
diff --git a/Tests/TestFiles/Reader/P_XXM_0519_01.3mf b/Tests/TestFiles/Reader/P_XXM_0519_01.3mf
new file mode 100644
index 000000000..cf19de339
Binary files /dev/null and b/Tests/TestFiles/Reader/P_XXM_0519_01.3mf differ