diff --git a/debian-stretch-titan/Dockerfile b/debian-stretch-titan/Dockerfile
index 0f4f17e2..39ff76f4 100644
--- a/debian-stretch-titan/Dockerfile
+++ b/debian-stretch-titan/Dockerfile
@@ -52,6 +52,12 @@ RUN	DPKG_ARCH="$(dpkg --print-architecture)" && export $DPKG_ARCH && \
 RUN	git config --global user.email docker@dock.er && \
 	git config --global user.name "Dock Er"
 
-# clone osmo-ttcn3-hacks and deps
+# clone osmo-ttcn3-hacks and deps, invalidate cache if deps change (OS#5017)
 RUN	git clone git://git.osmocom.org/osmo-ttcn3-hacks.git && \
 	make -C /osmo-ttcn3-hacks deps
+ADD	https://git.osmocom.org/osmo-ttcn3-hacks/plain/deps/Makefile /tmp/deps-Makefile
+RUN	if ! diff -q /tmp/deps-Makefile /osmo-ttcn3-hacks/deps/Makefile; then \
+		cd /osmo-ttcn3-hacks && \
+		git pull && \
+		make deps; \
+	fi