diff --git a/ext/mbstring/mbstring.dsp b/ext/mbstring/mbstring.dsp
index 63a7fa65675..629b0bd4d94 100644
--- a/ext/mbstring/mbstring.dsp
+++ b/ext/mbstring/mbstring.dsp
@@ -366,6 +366,10 @@ SOURCE=.\libmbfl\filters\mbfilter_koi8r.c
 # End Source File
 # Begin Source File
 
+SOURCE=.\libmbfl\filters\mbfilter_koi8u.c
+# End Source File
+# Begin Source File
+
 SOURCE=.\libmbfl\filters\mbfilter_armscii8.c
 # End Source File
 # Begin Source File
@@ -675,6 +679,10 @@ SOURCE=.\libmbfl\filters\mbfilter_koi8r.h
 # End Source File
 # Begin Source File
 
+SOURCE=.\libmbfl\filters\mbfilter_koi8u.h
+# End Source File
+# Begin Source File
+
 SOURCE=.\libmbfl\filters\mbfilter_armscii8.h
 # End Source File
 # Begin Source File
@@ -895,6 +903,10 @@ SOURCE=.\libmbfl\filters\unicode_table_koi8r.h
 # End Source File
 # Begin Source File
 
+SOURCE=.\libmbfl\filters\unicode_table_koi8u.h
+# End Source File
+# Begin Source File
+
 SOURCE=.\libmbfl\filters\unicode_table_armscii8.h
 # End Source File
 # Begin Source File