diff --git a/Makefile.in b/Makefile.in
index b043fc9..1e479ab 100644
--- a/Makefile.in
+++ b/Makefile.in
@@ -280,7 +280,7 @@ install-doc: doc
 	done
 
 test: binaries libraries
-	$(TCLSH) `@CYGPATH@ $(srcdir)/tests/all.tcl` $(TESTFLAGS) \
+	$(TCLSH) -encoding utf-8 `@CYGPATH@ $(srcdir)/tests/all.tcl` $(TESTFLAGS) \
 		-load "package ifneeded $(PACKAGE_NAME) $(PACKAGE_VERSION) \
 			[list load `@CYGPATH@ $(PKG_LIB_FILE)` [string totitle $(PACKAGE_NAME)]]"
 
@@ -292,14 +292,14 @@ gdb:
 
 gdb-test: binaries libraries
 	$(TCLSH_ENV) $(PKG_ENV) $(GDB) \
-	    --args $(TCLSH_PROG) `@CYGPATH@ $(srcdir)/tests/all.tcl` \
+	    --args $(TCLSH_PROG) -encoding utf-8 `@CYGPATH@ $(srcdir)/tests/all.tcl` \
 	    $(TESTFLAGS) -singleproc 1 \
 	    -load "package ifneeded Thread $(PACKAGE_VERSION) \
 		[list load `@CYGPATH@ $(PKG_LIB_FILE)` [string totitle $(PACKAGE_NAME)]]"
 
 valgrind: binaries libraries
 	$(TCLSH_ENV) $(PKG_ENV) $(VALGRIND) $(VALGRINDARGS) $(TCLSH_PROG) \
-	    `@CYGPATH@ $(srcdir)/tests/all.tcl` $(TESTFLAGS)
+	    -encoding utf-8 `@CYGPATH@ $(srcdir)/tests/all.tcl` $(TESTFLAGS)
 
 valgrindshell: binaries libraries
 	$(TCLSH_ENV) $(PKG_ENV) $(VALGRIND) $(VALGRINDARGS) $(TCLSH_PROG) $(SCRIPT)