diff --git a/Makefile b/Makefile
index 560defa..4307ca0 100644
--- a/Makefile
+++ b/Makefile
@@ -1,4 +1,5 @@
-CXXFLAGS += -std=c++17 -g3 -ggdb -O0
+CXXFLAGS += -std=c++17 -g3 -ggdb -O0 \
+            -Wall -Wextra -pedantic -Wno-vla -Werror
 
 CXXFILES := corewords.cpp dictionary.cpp parser.cpp state.cpp types.cpp
 OBJFILES := $(subst .cpp,.o,$(CXXFILES))
diff --git a/dictionary.cpp b/dictionary.cpp
index de10303..1ac2839 100644
--- a/dictionary.cpp
+++ b/dictionary.cpp
@@ -115,7 +115,7 @@ Word Dictionary::input()
 
 bool Dictionary::equal(Word word, std::string_view sv) const
 {
-    if (sv.size() != word.end - word.start)
+    if (sv.size() != static_cast<Addr>(word.end - word.start))
         return false;
 
     for (unsigned i = 0; i < sv.size(); ++i) {