diff --git a/tcl.spec b/tcl.spec
index d4c4b8b..2e33571 100644
--- a/tcl.spec
+++ b/tcl.spec
@@ -91,6 +91,20 @@ eval $MAKE
 # Some of the regressioin tests write to $HOME, so better redirect them
 mkdir home
 export HOME=$PWD/home
+# Run the testsuite to gather some data for the profile-based
+# optimisation and let rpmbuild fail on unexpected test failures.
+cat > known-failures <<EOF
+httpold-4.12
+mathop-25.14
+EOF
+eval $MAKE test 2>&1 | tee testresults
+grep FAILED testresults | grep -Fqvf known-failures && exit 1
+# If we don't do profile based optimisation, we are done at this point.
+test -z "$PFLAGS" && exit 0
+# Rebuild and use the profiling results
+make clean
+PFLAGS="%cflags_profile_feedback"
+eval $MAKE
 
 %install
 make -C unix install install-private-headers \