diff --git a/Makefile b/Makefile
index 804990ce8..1bd79e6de 100644
--- a/Makefile
+++ b/Makefile
@@ -18,7 +18,10 @@ CFLAGS=\
 	-g \
 	-I$(PYTHONINCLUDE) \
 	-fPIC \
+	-Wall \
 	-Wno-warn-absolute-paths \
+	-Werror=unused-variable \
+	-Werror=sometimes-uninitialized \
 	-Werror=int-conversion \
 	-Werror=incompatible-pointer-types \
 	$(EXTRA_CFLAGS)
@@ -135,7 +138,7 @@ benchmark: all
 
 clean:
 	rm -fr build/*
-	rm -fr src/*.o
+	rm -fr src/*/*.o
 	rm -fr node_modules
 	make -C packages clean
 	echo "The Emsdk, CPython are not cleaned. cd into those directories to do so."
diff --git a/src/core/error_handling.c b/src/core/error_handling.c
index b242577fa..a2c1bd19c 100644
--- a/src/core/error_handling.c
+++ b/src/core/error_handling.c
@@ -94,7 +94,7 @@ wrap_exception(bool attach_python_error)
   PyObject* type = NULL;
   PyObject* value = NULL;
   PyObject* traceback = NULL;
-  PyObject* pystr;
+  PyObject* pystr = NULL;
   JsRef pyexc_proxy = NULL;
   JsRef jserror = NULL;
 
diff --git a/src/core/jsproxy.c b/src/core/jsproxy.c
index 64f83045c..2602c2d30 100644
--- a/src/core/jsproxy.c
+++ b/src/core/jsproxy.c
@@ -200,8 +200,6 @@ finally:
 static PyObject*
 JsProxy_RichCompare(PyObject* a, PyObject* b, int op)
 {
-  JsProxy* aproxy = (JsProxy*)a;
-
   if (!JsProxy_Check(b)) {
     switch (op) {
       case Py_EQ:
@@ -820,6 +818,13 @@ JsMethod_Vectorcall(PyObject* self,
                     PyObject* kwnames)
 {
   bool kwargs = false;
+  bool success = false;
+  JsRef idargs = NULL;
+  JsRef idkwargs = NULL;
+  JsRef idarg = NULL;
+  JsRef idresult = NULL;
+  PyObject* pyresult = NULL;
+
   if (kwnames != NULL) {
     // There were kwargs? But maybe kwnames is the empty tuple?
     PyObject* kwname = PyTuple_GetItem(kwnames, 0); /* borrowed!*/
@@ -848,12 +853,6 @@ JsMethod_Vectorcall(PyObject* self,
 
   // Recursion error?
   FAIL_IF_NONZERO(Py_EnterRecursiveCall(" in JsProxy_Vectorcall"));
-  bool success = false;
-  JsRef idargs = NULL;
-  JsRef idkwargs = NULL;
-  JsRef idarg = NULL;
-  JsRef idresult = NULL;
-  PyObject* pyresult = NULL;
 
   Py_ssize_t nargs = PyVectorcall_NARGS(nargsf);
   idargs = hiwire_array();
diff --git a/src/core/python2js.c b/src/core/python2js.c
index bbb61fa6e..1fdb927b7 100644
--- a/src/core/python2js.c
+++ b/src/core/python2js.c
@@ -192,7 +192,6 @@ static JsRef
 _python2js_set(PyObject* x, PyObject* cache, int depth)
 {
   bool success = false;
-  bool cached = false;
   PyObject* iter = NULL;
   PyObject* pykey = NULL;
   JsRef jskey = NULL;