Index: win/rules.vc
===================================================================
diff -u -rb9a6a8fbb41ba8403d78c43191c8372c574c8ebf -rc50977864d18f1c8f049acc7679c0e8eb988968a
--- win/rules.vc	(.../rules.vc)	(revision b9a6a8fbb41ba8403d78c43191c8372c574c8ebf)
+++ win/rules.vc	(.../rules.vc)	(revision c50977864d18f1c8f049acc7679c0e8eb988968a)
@@ -1077,12 +1077,21 @@
 
 !if $(TCLINSTALL) # Building against an installed Tcl
 
-TCLSH		= $(_TCLDIR)\bin\tclsh$(TCL_VERSION)$(SUFX).exe
-!if !exist("$(TCLSH)") && $(TCL_THREADS)
-TCLSH           = $(_TCLDIR)\bin\tclsh$(TCL_VERSION)t$(SUFX).exe
+# When building extensions, we need to locate tclsh. Depending on version
+# of Tcl we are building against, this may or may not have a "t" suffix.
+# Try various possibilities in turn.
+TCLSH		= $(_TCLDIR)\bin\tclsh$(TCL_VERSION)$(SUFX:t=).exe
+!if !exist("$(TCLSH)")
+TCLSH           = $(_TCLDIR)\bin\tclsh$(TCL_VERSION)t$(SUFX:t=).exe
 !endif
+
 TCLSTUBLIB	= $(_TCLDIR)\lib\tclstub$(TCL_VERSION).lib
-TCLIMPLIB	= $(_TCLDIR)\lib\tcl$(TCL_VERSION)$(SUFX).lib
+TCLIMPLIB	= $(_TCLDIR)\lib\tcl$(TCL_VERSION)$(SUFX:t=).lib
+# When building extensions, may be linking against Tcl that does not add
+# "t" suffix (e.g. 8.5 or 8.7). If lib not found check for that possibility.
+!if !exist("$(TCLIMPLIB)")
+TCLIMPLIB	= $(_TCLDIR)\lib\tcl$(TCL_VERSION)t$(SUFX:t=).lib
+!endif
 TCL_LIBRARY	= $(_TCLDIR)\lib
 TCLREGLIB	= $(_TCLDIR)\lib\tclreg13$(SUFX:t=).lib
 TCLDDELIB	= $(_TCLDIR)\lib\tcldde14$(SUFX:t=).lib
@@ -1091,12 +1100,17 @@
 
 !else # Building against Tcl sources
 
-TCLSH		= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclsh$(TCL_VERSION)$(SUFX).exe
-!if !exist($(TCLSH)) && $(TCL_THREADS)
-TCLSH		= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclsh$(TCL_VERSION)t$(SUFX).exe
+TCLSH		= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclsh$(TCL_VERSION)$(SUFX:t=).exe
+!if !exist($(TCLSH))
+TCLSH		= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclsh$(TCL_VERSION)t$(SUFX:t=).exe
 !endif
 TCLSTUBLIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclstub$(TCL_VERSION).lib
-TCLIMPLIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tcl$(TCL_VERSION)$(SUFX).lib
+TCLIMPLIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tcl$(TCL_VERSION)$(SUFX:t=).lib
+# When building extensions, may be linking against Tcl that does not add
+# "t" suffix (e.g. 8.5 or 8.7). If lib not found check for that possibility.
+!if !exist("$(TCLIMPLIB)")
+TCLIMPLIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tcl$(TCL_VERSION)t$(SUFX:t=).lib
+!endif
 TCL_LIBRARY	= $(_TCLDIR)\library
 TCLREGLIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tclreg13$(SUFX:t=).lib
 TCLDDELIB	= $(_TCLDIR)\win\$(BUILDDIRTOP)\tcldde14$(SUFX:t=).lib