diff --git a/Makefile b/Makefile
index 4d1b52d51..db8cbd316 100644
--- a/Makefile
+++ b/Makefile
@@ -1,7 +1,9 @@
 # This file is generated by tools/dmake, do not edit.
 
 # To compile without rules, use 'make HAVE_RULES=no'
-HAVE_RULES = yes
+ifndef HAVE_RULES
+    HAVE_RULES=yes
+endif
 
 ifndef CXXFLAGS
     CXXFLAGS=-Wall -Wextra -Wshadow -pedantic -Wno-long-long -Wfloat-equal -Wcast-qual -D_GLIBCXX_DEBUG -g
diff --git a/tools/dmake.cpp b/tools/dmake.cpp
index 1a1625862..c7745cb7c 100644
--- a/tools/dmake.cpp
+++ b/tools/dmake.cpp
@@ -218,8 +218,8 @@ int main(int argc, char **argv)
     }
 
     fout << "# This file is generated by tools/dmake, do not edit.\n\n";
-    fout << "# To compile without rules, use 'make HAVE_RULES=no'\n"
-         << "HAVE_RULES = yes\n\n";
+    fout << "# To compile without rules, use 'make HAVE_RULES=no'\n";
+    makeConditionalVariable(fout, "HAVE_RULES", "yes");
 
     // Makefile settings..
     if (release)