diff --git a/src/Floating.cpp b/src/Floating.cpp
index 531a066b2c..513c4fac34 100644
--- a/src/Floating.cpp
+++ b/src/Floating.cpp
@@ -16,6 +16,7 @@
 
 #include "support/debug.h"
 #include "support/lstrings.h"
+#include "support/textutils.h"
 
 using namespace std;
 
@@ -67,9 +68,9 @@ string Floating::defaultCSSClass() const
 	string::const_iterator it = n.begin();
 	string::const_iterator en = n.end();
 	for (; it != en; ++it) {
-		if (!isalpha(*it))
+		if (!isAlphaASCII(*it))
 			d += "_";
-		else if (islower(*it))
+		else if (isLower(*it))
 			d += *it;
 		else
 			d += support::lowercase(*it);
diff --git a/src/Layout.cpp b/src/Layout.cpp
index 1606977779..120f7a2c3e 100644
--- a/src/Layout.cpp
+++ b/src/Layout.cpp
@@ -1009,7 +1009,7 @@ string Layout::defaultCSSClass() const
 				d = from_ascii("lyx_");
 			else
 				d += '_';
-		} else if (islower(c))
+		} else if (isLower(c))
 			d += c;
 		else
 			// this is slow, so do it only if necessary
diff --git a/src/insets/InsetLayout.cpp b/src/insets/InsetLayout.cpp
index dee7e29f7a..c87ebac7b0 100644
--- a/src/insets/InsetLayout.cpp
+++ b/src/insets/InsetLayout.cpp
@@ -20,6 +20,7 @@
 
 #include "support/debug.h"
 #include "support/lstrings.h"
+#include "support/textutils.h"
 
 #include <vector>
 
@@ -426,9 +427,9 @@ string InsetLayout::defaultCSSClass() const
 	string::const_iterator it = n.begin();
 	string::const_iterator en = n.end();
 	for (; it != en; ++it) {
-		if (!isalpha(*it))
+		if (!isAlphaASCII(*it))
 			d += "_";
-		else if (islower(*it))
+		else if (isLower(*it))
 			d += *it;
 		else
 			d += support::lowercase(*it);
diff --git a/src/mathed/InsetMathChar.cpp b/src/mathed/InsetMathChar.cpp
index ae1a3b03ee..e23723ca8d 100644
--- a/src/mathed/InsetMathChar.cpp
+++ b/src/mathed/InsetMathChar.cpp
@@ -193,7 +193,7 @@ void InsetMathChar::mathmlize(MathStream & ms) const
 	}		
 
 	char const * type = 
-		(isalpha(char_) || Encodings::isMathAlpha(char_))
+		(isAlphaASCII(char_) || Encodings::isMathAlpha(char_))
 			? "mi" : "mo";
 	// we don't use MTag and ETag because we do not want the spacing
 	ms << "<" << type << ">" << char_type(char_) << "</" << type << ">";	
@@ -227,7 +227,7 @@ void InsetMathChar::htmlize(HtmlStream & ms) const
 		return;
 	}		
 
-	if (isalpha(char_) || Encodings::isMathAlpha(char_))
+	if (isAlphaASCII(char_) || Encodings::isMathAlpha(char_))
 		// we don't use MTag and ETag because we do not want the spacing
 		ms << MTag("i") << char_type(char_) << ETag("i");
 	else
diff --git a/src/output_xhtml.cpp b/src/output_xhtml.cpp
index 005aa42a04..4a587ee5ea 100644
--- a/src/output_xhtml.cpp
+++ b/src/output_xhtml.cpp
@@ -125,7 +125,7 @@ string cleanAttr(string const & str)
 	string::const_iterator it = str.begin();
 	string::const_iterator en = str.end();
 	for (; it != en; ++it)
-		newname += isalnum(*it) ? *it : '_';
+		newname += isAlnumASCII(*it) ? *it : '_';
 	return newname;	
 }
 
diff --git a/status.20x b/status.20x
index 46bba5f6bb..0959093c53 100644
--- a/status.20x
+++ b/status.20x
@@ -75,6 +75,8 @@ What's new
 
 * DOCUMENT INPUT/OUTPUT
 
+- Fixed assertions on Windows for XHTML output (bug 8078).
+
 - Fix reconfiguration on Windows when the user directory is a UNC path
   (bug 8098).