diff --git a/pkgs/development/interpreters/tcl/builder.sh b/pkgs/development/interpreters/tcl/builder.sh
index c1abbf2fc91..24d4853de5d 100644
--- a/pkgs/development/interpreters/tcl/builder.sh
+++ b/pkgs/development/interpreters/tcl/builder.sh
@@ -7,6 +7,7 @@ preConfigure() {
 preConfigure=preConfigure
 
 postInstall() {
+        make install-private-headers
 	ln -s $out/bin/tclsh8.4 $out/bin/tclsh
 }