diff --git a/.github/workflows/test.yaml b/.github/workflows/test.yaml
index 5e110f80..bcf41095 100644
--- a/.github/workflows/test.yaml
+++ b/.github/workflows/test.yaml
@@ -45,10 +45,10 @@ jobs:
             rebar3: "3.16.1"
           - otp: "25.3.2.15"
             rebar3: "3.22.1"
-          # - otp: "26.2.5.5"
-          #   rebar3: "3.22.1"
-          # - otp: "27.1.2"
-          #   rebar3: "3.22.1"
+          - otp: "26.2.5.5"
+            rebar3: "3.22.1"
+          - otp: "27.1.2"
+            rebar3: "3.22.1"
     steps:
       - name: Install Emacs
         uses: purcell/setup-emacs@master
diff --git a/Makefile b/Makefile
index af210c31..7c1a9750 100644
--- a/Makefile
+++ b/Makefile
@@ -29,10 +29,10 @@ rel/releases:
 
 deps/mochiweb/src:
 	$(GIT) clone "https://github.com/mochi/mochiweb" deps/mochiweb
-	cd deps/mochiweb && $(GIT) checkout --detach 835b107a4da4550080d032623ff6ae9a18d02c37
+	cd deps/mochiweb && $(GIT) checkout --detach 611254eb941e502227f221667389b98fd8e72d6f
 deps/meck/src:
 	$(GIT) clone "https://github.com/eproxus/meck" deps/meck
-	cd deps/meck && $(GIT) checkout --detach cc47aab4b64a46a5409c1a93353d44a367b41454
+	cd deps/meck && $(GIT) checkout --detach 59d61d87b42408779e7863b6e8544325bcf90efd
 
 deps/mochiweb: deps/mochiweb/src deps/mochiweb/ebin
 deps/meck: deps/meck/src deps/meck/ebin
@@ -68,7 +68,8 @@ erlang.plt:
 	$(DIALYZER) --quiet --build_plt --output_plt $@ --apps \
 		erts kernel stdlib mnesia crypto sasl eunit \
 		syntax_tools compiler tools debugger dialyzer \
-		wx runtime_tools
+		wx runtime_tools ssl public_key asn1 inets xmerl \
+		parsetools
 edts.plt: erlang.plt
 	$(DIALYZER) --add_to_plt --plt erlang.plt -r lib/ deps/ --output_plt $@
 
@@ -78,17 +79,17 @@ manual-tests: $(OTP_TESTS) byte-compilation-test
 
 .PHONY: integration-tests
 integration-tests: all test-projects
-	$(EMACS) -Q --batch \
-	-L $(ERLANG_EMACS_LIB) \
-	-l test_data/load-tests.el \
+	$(EMACS) --quick --batch \
+	--directory $(ERLANG_EMACS_LIB) \
+	--load test_data/load-tests.el \
 	--debug-init \
-	-f edts-test-run-suites-batch-and-exit
+	--funcall edts-test-run-suites-batch-and-exit
 
 .PHONY: ert
 ert: test-projects
-	$(EMACS) -Q --batch \
-	-L $(ERLANG_EMACS_LIB) \
-	-l test_data/load-tests.el \
+	$(EMACS) --quick --batch \
+	--directory $(ERLANG_EMACS_LIB) \
+	--load test_data/load-tests.el \
 	--debug-init \
 	--eval "(ert-run-tests-batch-and-exit '(not (tag edts-test-suite)))"
 
@@ -108,8 +109,10 @@ byte-compilation-test:
 	-u $(shell id -u) \
 	silex/emacs \
 	/bin/bash -c \
-	'emacs -Q --batch -L ${PWD} -l test_data/package-install-deps.el \
-	-f batch-byte-compile *.el elisp/edts/*.el lib/**/*.el'
+	'emacs --quick --batch \
+	--directory ${PWD} \
+	--load test_data/package-install-deps.el \
+	--funcall batch-byte-compile *.el elisp/edts/*.el lib/**/*.el'
 
 .PHONY: $(OTP_TESTS)
 $(OTP_TESTS):
diff --git a/lib/edts_dialyzer/src/edts_dialyzer.erl b/lib/edts_dialyzer/src/edts_dialyzer.erl
index 0fb36f50..1ce5e55d 100644
--- a/lib/edts_dialyzer/src/edts_dialyzer.erl
+++ b/lib/edts_dialyzer/src/edts_dialyzer.erl
@@ -168,9 +168,7 @@ create_plt(BasePlt0, OutPlt, Files) ->
   BasePlt =
     case BasePlt0 of
       undefined ->
-        try dialyzer_plt:get_default_plt()
-        catch throw:{dialyzer_error, _} -> undefined
-        end;
+        try_get_default_plt();
       _ when is_list(BasePlt0) -> BasePlt0
     end,
   VarOpts =
@@ -181,6 +179,22 @@ create_plt(BasePlt0, OutPlt, Files) ->
 
   dialyzer:run(BaseOpts ++ VarOpts).
 
+-ifndef(OTP_RELEASE). % OTP-19 and lesser
+-def(OTP_RELEASE, 1).
+-endif.
+
+-if(?OTP_RELEASE >= 26).
+try_get_default_plt() ->
+    try dialyzer_iplt:get_default_iplt_filename()
+    catch throw:{dialyzer_error, _} -> undefined
+    end.
+-else.
+try_get_default_plt() ->
+    try dialyzer_plt:get_default_plt()
+    catch throw:{dialyzer_error, _} -> undefined
+    end.
+-endif.
+
 get_included_files(Plt) ->
   {ok, Info} = dialyzer:plt_info(Plt),
   {files, Files} = lists:keyfind(files, 1, Info),
diff --git a/test_data/manual/Dockerfile.otp26 b/test_data/manual/Dockerfile.otp26
index ef1cb7f3..00367514 100644
--- a/test_data/manual/Dockerfile.otp26
+++ b/test_data/manual/Dockerfile.otp26
@@ -1,4 +1,4 @@
-FROM ubuntu:22.04
+FROM ubuntu:20.04
 
 SHELL ["/bin/bash", "-c"]
 
@@ -11,7 +11,7 @@ RUN apt-get -q update && \
     rm -rf /var/lib/apt/lists/*
 
 ENV ERLANG_VERSION=26.0.2 \
-    ERLANG_EMACS_LIB="/usr/lib/erlang/lib/tools-3.5.3/emacs"
+    ERLANG_EMACS_LIB="/usr/lib/erlang/lib/tools-3.6/emacs"
 
 RUN . /etc/os-release && \
     export FILE="esl-erlang_${ERLANG_VERSION}-1~ubuntu~${VERSION_CODENAME}_amd64.deb" && \
@@ -23,6 +23,5 @@ WORKDIR /edts
 
 COPY . .
 
-RUN make
-#  && \
-    # make test
+RUN make && \
+    make test
diff --git a/test_data/manual/Dockerfile.otp27 b/test_data/manual/Dockerfile.otp27
new file mode 100644
index 00000000..ce532fab
--- /dev/null
+++ b/test_data/manual/Dockerfile.otp27
@@ -0,0 +1,20 @@
+FROM erlang:27.1.2
+
+SHELL ["/bin/bash", "-c"]
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+RUN apt-get -q update && \
+    apt-get -yq install \
+      wget \
+      emacs git && \
+    rm -rf /var/lib/apt/lists/*
+
+ENV ERLANG_EMACS_LIB="/usr/local/lib/erlang/lib/tools-4.1/emacs"
+
+WORKDIR /edts
+
+COPY . .
+
+RUN make && \
+    make test