diff --git a/tests/aiger/generate_mk.py b/tests/aiger/generate_mk.py
index e6f3f4091..47e94884a 100644
--- a/tests/aiger/generate_mk.py
+++ b/tests/aiger/generate_mk.py
@@ -55,11 +55,6 @@ def create_tests():
     ]))
 
 extra = [
-    "ifneq ($(ABCEXTERNAL),)",
-    "ABC ?= $(ABCEXTERNAL)",
-    "else",
-    f"ABC ?= {gen_tests_makefile.yosys_basedir}/yosys-abc",
-    "endif",
     "SHELL := /usr/bin/env bash",
 ]
 
diff --git a/tests/common.mk b/tests/common.mk
index 59ea599c0..1636a880b 100644
--- a/tests/common.mk
+++ b/tests/common.mk
@@ -5,10 +5,12 @@ YOSYS ?= $(BUILD_DIR)/yosys
 ABC   ?= $(BUILD_DIR)/yosys-abc
 YOSYS_FILTERLIB ?= $(BUILD_DIR)/yosys-filterlib
 YOSYS_CONFIG ?= $(BUILD_DIR)/yosys-config
+YOSYS_MAX_THREADS ?= 4
 
 export YOSYS
 export YOSYS_CONFIG
 export ABC
+export YOSYS_MAX_THREADS
 
 all:
 
diff --git a/tests/gen_tests_makefile.py b/tests/gen_tests_makefile.py
index 77602a9a0..034883a2c 100644
--- a/tests/gen_tests_makefile.py
+++ b/tests/gen_tests_makefile.py
@@ -94,12 +94,6 @@ def generate_tests(argv, cmds):
 
 def print_header(extra=None):
     print(f"include {common_mk}")
-    print(f"ifneq ($(wildcard {yosys_basedir}/Makefile.conf),)")
-    print(f"include {yosys_basedir}/Makefile.conf")
-    print(f"endif")
-
-    print("")
-    print("export YOSYS_MAX_THREADS := 4")
     if extra:
         for line in extra:
             print(line)