diff --git a/tests/conftest.py b/tests/conftest.py
index 09e82868b571f378e3ebcb1f04fc3a4951a0034a..3e98fcef97a31ab7141164c58edef90440e18949 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -50,8 +50,7 @@ include $(E3_REQUIRE_TOOLS)/driver.makefile
     def add_file(self, name):
         (self.module_dir / name).touch()
 
-    def add_to_makefile(self, makefile_var, value, modifier="+"):
-        assert modifier in ["", "+", "?", ":", "!"]
+    def add_var_to_makefile(self, makefile_var, value, modifier="+"):
         with open(self.makefile, "a") as f:
             f.write(f"{makefile_var} {modifier}= {value}\n")
 
diff --git a/tests/test_build.py b/tests/test_build.py
index fadcef824f25b363be235c5a8156d550bf3abfc4..a7932e64c1af5748495345e58586b68fc46c3d2b 100644
--- a/tests/test_build.py
+++ b/tests/test_build.py
@@ -67,7 +67,7 @@ def test_patch(wrapper):
 
 
 def test_missing_dbd_file(wrapper):
-    wrapper.add_to_makefile("DBDS", "nonexistent.dbd")
+    wrapper.add_var_to_makefile("DBDS", "nonexistent.dbd")
     rc, _, errs = run_make(wrapper, "build")
 
     assert rc == 2
@@ -78,7 +78,7 @@ def test_missing_dbd_file(wrapper):
 
 
 def test_missing_source_file(wrapper):
-    wrapper.add_to_makefile("SOURCES", "nonexistent.c")
+    wrapper.add_var_to_makefile("SOURCES", "nonexistent.c")
     rc, _, errs = run_make(wrapper, "build")
 
     assert rc == 2
@@ -89,7 +89,7 @@ def test_missing_source_file(wrapper):
 
 
 def test_missing_requirement(wrapper):
-    wrapper.add_to_makefile("REQUIRED", "foo")
+    wrapper.add_var_to_makefile("REQUIRED", "foo")
 
     rc, _, errs = run_make(wrapper, "build")
     assert rc == 2
@@ -102,8 +102,8 @@ def test_header_install_location(wrapper):
 
     extensions = ["h", "hpp", "hxx", "hh"]
     for ext in extensions:
-        wrapper.add_to_makefile("HEADERS", f"db/subdir/header.{ext}")
-    wrapper.add_to_makefile("KEEP_HEADER_SUBDIRS", "db")
+        wrapper.add_var_to_makefile("HEADERS", f"db/subdir/header.{ext}")
+    wrapper.add_var_to_makefile("KEEP_HEADER_SUBDIRS", "db")
 
     for ext in extensions:
         (subdir / f"header.{ext}").touch()
@@ -126,8 +126,8 @@ def test_updated_dependencies(wrappers):
 
     old_version = "0.0.0+0"
 
-    wrapper_main.add_to_makefile("REQUIRED", wrapper_dep.name)
-    wrapper_main.add_to_makefile(
+    wrapper_main.add_var_to_makefile("REQUIRED", wrapper_dep.name)
+    wrapper_main.add_var_to_makefile(
         f"{wrapper_dep.name}_VERSION", old_version, modifier=""
     )
 
@@ -152,7 +152,7 @@ def test_updated_dependencies(wrappers):
     )
     assert rc == 0
 
-    wrapper_main.add_to_makefile(
+    wrapper_main.add_var_to_makefile(
         f"{wrapper_dep.name}_VERSION", new_version, modifier=""
     )